U.S. patent application number 16/478218 was filed with the patent office on 2020-01-30 for ultrasonic bonding apparatus, ultrasonic bonding inspection method and ultrasonically-bonded portion fabrication method.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Minoru EGUSA, Kazuyuki HASHIMOTO, Shingo SUDO, Erubi SUZUKI.
Application Number | 20200035642 16/478218 |
Document ID | / |
Family ID | 63039858 |
Filed Date | 2020-01-30 |
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United States Patent
Application |
20200035642 |
Kind Code |
A1 |
EGUSA; Minoru ; et
al. |
January 30, 2020 |
ULTRASONIC BONDING APPARATUS, ULTRASONIC BONDING INSPECTION METHOD
AND ULTRASONICALLY-BONDED PORTION FABRICATION METHOD
Abstract
An ultrasonic bonding apparatus includes an ultrasonic bonding
machine having an ultrasonic tool for applying an ultrasonic wave
to a bonding target member mounted on a fixed object fixed to a
jig, while pressing a bonding member against the bonding target
member; and a bonding inspection apparatus for inspecting a bonding
quality of the bonding target member and the bonding member. The
bonding inspection apparatus includes: a bonded-state measuring
device for detecting a vibration in the jig or a housing of the
ultrasonic bonding machine equipped with the jig, to thereby output
a detection signal; and a bonded-state determination device for
determining, in a bonding process for the bonding target member and
the bonding member, a bonded state between the bonding target
member and the bonding member on the basis of the detection signal
outputted by the bonded-state measuring device.
Inventors: |
EGUSA; Minoru; (Tokyo,
JP) ; SUDO; Shingo; (Tokyo, JP) ; HASHIMOTO;
Kazuyuki; (Tamba-shi, Hyogo, JP) ; SUZUKI; Erubi;
(Tamba-shi, Hyogo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Chiyoda-ku, Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Chiyoda-ku, Tokyo
JP
|
Family ID: |
63039858 |
Appl. No.: |
16/478218 |
Filed: |
February 2, 2018 |
PCT Filed: |
February 2, 2018 |
PCT NO: |
PCT/JP2018/003605 |
371 Date: |
July 16, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B06B 3/00 20130101; G01H
3/04 20130101; H01L 24/48 20130101; G01N 29/14 20130101; H01L
2224/85205 20130101; H01L 24/45 20130101; H01L 2224/32225 20130101;
H01L 2224/859 20130101; H01L 24/75 20130101; H01L 24/29 20130101;
H01L 2224/48137 20130101; H01L 24/32 20130101; G01H 11/08 20130101;
G01H 17/00 20130101; H01L 2224/291 20130101; H01L 23/053 20130101;
H01L 25/07 20130101; H01L 2224/48472 20130101; G01H 5/00 20130101;
H01L 24/85 20130101; H01L 2224/48227 20130101; H01L 2924/3511
20130101; B23K 20/10 20130101; H01L 24/73 20130101; H01L 2224/45124
20130101; H01L 2224/73265 20130101; H01L 2924/19107 20130101; B23K
31/125 20130101; H01L 23/24 20130101; H01L 23/49811 20130101; H01L
2224/48091 20130101; H01L 2224/48091 20130101; H01L 2924/00014
20130101; H01L 2224/45124 20130101; H01L 2924/00014 20130101; H01L
2224/291 20130101; H01L 2924/014 20130101; H01L 2924/00014
20130101; H01L 2224/73265 20130101; H01L 2224/32225 20130101; H01L
2224/48227 20130101; H01L 2924/00012 20130101 |
International
Class: |
H01L 23/00 20060101
H01L023/00; G01H 17/00 20060101 G01H017/00; B23K 20/10 20060101
B23K020/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2017 |
JP |
2017-018138 |
Claims
1. An ultrasonic bonding apparatus for bonding a bonding target
member and a bonding member together using an ultrasonic wave,
comprising: an ultrasonic bonding machine having an ultrasonic tool
for applying the ultrasonic wave to the bonding target member
mounted on a fixed object fixed to a jig, while pressing the
bonding member against the bonding target member; and a bonding
inspection apparatus for inspecting a bonding quality of the
bonding target member and the bonding member; wherein the bonding
inspection apparatus comprises: a bonded-state measuring device for
detecting a vibration propagating in the jig or a housing of the
ultrasonic bonding machine equipped with the jig, using a sensor
that is fixed to the jig or the housing at a position at which it
does not make contact with the bonding target member and the
bonding member and that detects the vibration, to thereby output a
detection signal; and a bonded-state determination device for
determining, in a bonding process for the bonding target member and
the bonding member, a bonded state between the bonding target
member and the bonding member on the basis of a frequency component
that is found, in an arithmetically-processed waveform obtained
through numerical arithmetic processing from a waveform of the
detection signal outputted by the bonded-state measuring device, at
a frequency that is other than an application frequency of the
ultrasonic wave applied by the ultrasonic tool and frequencies that
are natural times said application frequency, and is higher than
said application frequency.
2.-20. (canceled)
21. An ultrasonic bonding apparatus for bonding a bonding target
member and a bonding member together using an ultrasonic wave,
comprising: an ultrasonic bonding machine having an ultrasonic tool
for applying the ultrasonic wave to the bonding target member
mounted on a fixed object fixed to a jig, while pressing the
bonding member against the bonding target member; and a bonding
inspection apparatus for inspecting a bonding quality of the
bonding target member and the bonding member; wherein the bonding
inspection apparatus comprises: a bonded-state measuring device for
detecting a vibration propagating in the jig or a housing of the
ultrasonic bonding machine equipped with the jig, using a sensor
that is fixed to the jig or the housing at a position at which it
does not make contact with the bonding target member and the
bonding member and that detects the vibration, to thereby output a
detection signal; and a bonded-state determination device for
determining, in a bonding process for the bonding target member and
the bonding member, a bonded state between the bonding target
member and the bonding member on the basis of the detection signal
outputted by the bonded-state measuring device; and wherein the jig
is formed of a material by which a sound velocity of the ultrasonic
wave propagating in that jig is 3000 m/s or more.
22. The ultrasonic bonding apparatus of claim 21, wherein the
bonded-state determination device determines the bonded state
between the bonding target member and the bonding member on the
basis of: a waveform of a reference detection signal which was
measured beforehand by the bonded-state measuring device when a
same bonding process as said bonding process was executed
beforehand in an ultrasonic bonding condition for bonding the
bonding target member and the bonding member together and whereby a
bonded state corresponding to the bonding target member and the
bonding member was determined to be non-defective; and a waveform
of the detection signal measured by the bonded-state measuring
device in said bonding process.
23. The ultrasonic bonding apparatus of claim 22, wherein the
bonded-state determination device comprises a signal processing
unit for generating a reference waveform as the waveform of the
reference detection signal and a detection waveform as the waveform
of the detection signal.
24. The ultrasonic bonding apparatus of claim 21, wherein the
bonded-state determination device determines the bonded state
between the bonding target member and the bonding member on the
basis of: an arithmetically-processed reference waveform obtained
through numerical arithmetic processing from a waveform of a
reference detection signal which was measured beforehand by the
bonded-state measuring device when a same bonding process as said
bonding process was executed beforehand in an ultrasonic bonding
condition for bonding the bonding target member and the bonding
member together and whereby a bonded state corresponding to the
bonding target member and the bonding member was determined to be
non-defective; and an arithmetically-processed waveform obtained
through numerical arithmetic processing from a waveform of the
detection signal measured by the bonded-state measuring device in
said bonding process.
25. The ultrasonic bonding apparatus of claim 21, wherein the
bonded-state determination device determines the bonded state
between the bonding target member and the bonding member on the
basis of: a waveform of a reference detection signal which was
measured beforehand by the bonded-state measuring device when a
same bonding process as said bonding process was executed
beforehand in an ultrasonic bonding condition for bonding the
bonding target member and the bonding member together and whereby a
bonded state corresponding to the bonding target member and the
bonding member was determined to be non-defective; and an
arithmetically-processed reference waveform obtained through
numerical arithmetic processing from the waveform of the reference
detection signal; and a waveform of the detection signal measured
by the bonded-state measuring device in said bonding process; and
an arithmetically-processed waveform obtained through numerical
arithmetic processing from the waveform of the detection
signal.
26. The ultrasonic bonding apparatus of claim 1, wherein the fixed
object is a power semiconductor device having a casing, the bonding
target member is a wiring pattern of the power semiconductor
device, and, in the bonding member, its portion to be bonded to the
bonding target member is placed inside the casing.
27. The ultrasonic bonding apparatus of claim 1, wherein the sensor
is fixed to the jig and the bonded-state measuring device detects
the vibration propagating in the jig.
28. The ultrasonic bonding apparatus of claim 1, wherein the
vibration is an acoustic emission and the bonded-state measuring
device comprises, as said sensor, an AE sensor that detects the
acoustic emission.
29. The ultrasonic bonding apparatus of claim 1, wherein the
bonded-state measuring device further comprises a non-contact
vibrometer for detecting a vibration of a measuring object vibrated
by the ultrasonic wave, and wherein the non-contact vibrometer
detects a vibration of at least one of the bonding target member,
the bonding member, the ultrasonic tool and the jig, to thereby
output a detection signal.
30. The ultrasonic bonding apparatus of claim 1, wherein the
ultrasonic bonding machine performs bonding between the bonding
target member and the bonding member after changing an ultrasonic
bonding condition in said bonding process on the basis of a
determination result determined by the bonded-state determination
device.
31. An ultrasonic bonding inspection method for inspecting a
bonding quality of a bonded portion obtained by bonding between a
bonding target member and a bonding member using an ultrasonic
wave, wherein the bonding target member is mounted on a fixed
object fixed to a jig, and wherein the fixed object is a power
semiconductor device having a casing, the bonding target member is
a wiring pattern of the power semiconductor device, said ultrasonic
bonding inspection method comprising: a detection signal monitoring
step of detecting, in a bonding process for the bonding target
member and the bonding member, a vibration propagating in the jig
or a housing of an ultrasonic bonding machine equipped with the
jig, to thereby output a detection signal; and a bonded-state
determination step of determining a bonded state between the
bonding target member and the bonding member on the basis of the
detection signal outputted in the detection signal monitoring
step.
32. The ultrasonic bonding inspection method of claim 31, wherein,
in the detection signal monitoring step, the vibration is detected
at a position not in contact with the bonding target member and the
bonding member.
33. The ultrasonic bonding inspection method of claim 31, wherein,
in the detection signal monitoring step, a vibration of at least
one of the bonding target member, the bonding member and an
ultrasonic tool for applying the ultrasonic wave, is further
detected in a contactless manner, and its detection signal is
outputted.
34. The ultrasonic bonding inspection method of claim 31, wherein,
in the bonded-state determination step, the bonded state between
the bonding target member and the bonding member is determined on
the basis of: a waveform of a reference detection signal which was
measured beforehand when a same bonding process as said bonding
process was executed beforehand in an ultrasonic bonding condition
for bonding the bonding target member and the bonding member
together and whereby a bonded state corresponding to the bonding
target member and the bonding member was determined to be
non-defective; and a waveform of the detection signal being
measured.
35. The ultrasonic bonding inspection method of claim 31, wherein,
in the bonded-state determination step, an arithmetically-processed
reference waveform is generated that is to be obtained through
numerical arithmetic processing from a waveform of a reference
detection signal which was measured beforehand when a same bonding
process as said bonding process was executed beforehand in an
ultrasonic bonding condition for bonding the bonding target member
and the bonding member together and whereby a bonded state
corresponding to the bonding target member and the bonding member
was determined to be non-defective; an arithmetically-processed
waveform is generated that is to be obtained through numerical
arithmetic processing from a waveform of the detection signal being
measured; and the bonded state between the bonding target member
and the bonding member is determined on the basis of the
arithmetically-processed reference waveform and the
arithmetically-processed waveform.
36. The ultrasonic bonding inspection method of claim 31, wherein,
in the bonded-state determination step, a waveform of a reference
detection signal which was measured beforehand when a same bonding
process as said bonding process was executed beforehand in an
ultrasonic bonding condition for bonding the bonding target member
and the bonding member together and whereby a bonded state
corresponding to the bonding target member and the bonding member
was determined to be non-defective, and a waveform of the detection
signal being measured, are generated; an arithmetically-processed
reference waveform is generated that is to be obtained through
numerical arithmetic processing from the waveform of the reference
detection signal; an arithmetically-processed waveform is generated
that is to be obtained through numerical arithmetic processing from
the waveform of the detection signal; and the bonded state between
the bonding target member and the bonding member is determined on
the basis of the waveform of the reference detection signal, the
arithmetically-processed reference waveform, the waveform of the
detection signal and the arithmetically-processed waveform.
37. The ultrasonic bonding inspection method of claim 31, wherein
the bonding member is a metal connecting wire; wherein said bonding
process includes an application-frequency changing step of
increasing an application frequency of the ultrasonic wave to be
applied by an ultrasonic tool of the ultrasonic bonding machine to
the bonding target member and the bonding member; and wherein, in
the bonded-state determination step, a frequency waveform is
generated through calculation from the waveform of the detection
signal being measured, so that, when a difference between a timing
at which a frequency of the frequency waveform varies and a timing
at which the application frequency varies in the
application-frequency changing step is more than a preset
determination value, the bonded state is determined to be
defective; and when a difference between a timing at which the
frequency of the frequency waveform varies and a timing at which
the application frequency varies in the application-frequency
changing step is equal to or less than the preset determination
value, the bonded state is determined to be non-defective.
38. An ultrasonically-bonded portion fabrication method of
fabricating an ultrasonically-bonded portion by bonding a bonding
target member and a bonding member together using an ultrasonic
wave, comprising: a bonding process of applying the ultrasonic wave
to the bonding target member mounted on a fixed object fixed to a
jig, while pressing the bonding member against the bonding target
member, to thereby form the ultrasonically-bonded portion; wherein
said bonding process comprises: the detection signal monitoring
step and the bonded-state determination step in the ultrasonic
bonding inspection method of claim 31; a bonding condition changing
step of determining, when the bonded-state between the bonding
target member and the bonding member has been determined to be
defective in the bonded-state determination step, whether or not
the ultrasonic bonding condition for the bonding target member and
the bonding member is changeable, and then changing the ultrasonic
bonding condition for the bonding target member and the bonding
member if the ultrasonic bonding condition is changeable; a bonding
continuing step of executing, when the bonding condition changing
step has been executed, the detection signal monitoring step and
the bonded-state determination step with the ultrasonic bonding
condition changed in the bonding condition changing step; a
non-defective bonding stopping step of stopping said bonding
process in operation for the bonding target member and the bonding
member if the bonded state between the bonding target member and
the bonding member has been determined to be non-defective in the
bonded-state determination step; and a defective bonding stopping
step of stopping said bonding process in operation for the bonding
target member and the bonding member if the ultrasonic bonding
condition has been determined to be not changeable in the bonding
condition changing step.
39. An ultrasonically-bonded portion fabrication method of
fabricating an ultrasonically-bonded portion by bonding a bonding
target member and a bonding member together using an ultrasonic
wave, wherein the bonding member is a metal connecting wire, said
ultrasonically-bonded portion fabrication method comprising: a
bonding process of applying the ultrasonic wave to the bonding
target member mounted on a fixed object fixed to a jig, while
pressing the bonding member against the bonding target member, to
thereby form the ultrasonically-bonded portion; wherein said
bonding process comprises: an application-frequency changing step
of increasing an application frequency of the ultrasonic wave to be
applied by an ultrasonic tool of an ultrasonic bonding machine to
the bonding target member and the bonding member; the detection
signal monitoring step and the bonded-state determination step in
the ultrasonic bonding inspection method of claim 31; a bonding
condition changing step of determining, when the bonded-state
between the bonding target member and the bonding member has been
determined to be defective in the bonded-state determination step,
whether or not the ultrasonic bonding condition for the bonding
target member and the bonding member is changeable, and then
changing the ultrasonic bonding condition for the bonding target
member and the bonding member if the ultrasonic bonding condition
is changeable; a bonding continuing step of executing, when the
bonding condition changing step has been executed, the detection
signal monitoring step and the bonded-state determination step with
the ultrasonic bonding condition changed in the bonding condition
changing step; a non-defective bonding stopping step of stopping
said bonding process in operation for the bonding target member and
the bonding member if the bonded state between the bonding target
member and the bonding member has been determined to be
non-defective in the bonded-state determination step; and a
defective bonding stopping step of stopping said bonding process in
operation for the bonding target member and the bonding member if
the ultrasonic bonding condition has been determined to be not
changeable in the bonding condition changing step; wherein, in the
bonded-state determination step, a frequency waveform is generated
through calculation from the waveform of the detection signal being
measured, so that, when a difference between a timing at which a
frequency of the frequency waveform varies and a timing at which
the application frequency varies in the application-frequency
changing step is more than a preset determination value, the bonded
state is determined to be defective; and when a difference between
a timing at which the frequency of the frequency waveform varies
and a timing at which the application frequency varies in the
application-frequency changing step is equal to or less than the
preset determination value, the bonded state is determined to be
non-defective.
Description
TECHNICAL FIELD
[0001] The present invention relates to an ultrasonic bonding
apparatus for ultrasonically bonding a bonding member to a bonding
target member, and an ultrasonic bonding inspection method for
inspecting a bonding quality of the bonding member ultrasonically
bonded to the bonding target member.
BACKGROUND ART
[0002] In Patent Document 1, there is disclosed a bonding
inspection method for inspecting a bonded portion obtained by
ultrasonic bonding between an electrode of a semiconductor element
mounted in a semiconductor device and a tape for bonding. The
bonding inspection method of Patent Document 1 is an inspection
method for precisely recognizing a void portion, etc. of a several
.mu.m level that can not be determined to be a bonding defect
immediately from waveform data, etc. at the time of bonding.
Specifically, the bonding inspection method of Patent Document 1 is
an inspection method in which, after completion of the bonding, an
ultrasonic wave is applied near the bonded portion and a vibration
due to the ultrasonic wave propagating from the ultrasonic-wave
applied portion is detected by way of heat or sound (AE (Acoustic
Emission))), so that the bonded state is recognized based on
detection data thus obtained.
[0003] In Patent Document 2, there is disclosed a bonding quality
inspection apparatus and a bonding quality inspection method for
inspecting, when an IGBT element and a wiring terminal are
ultrasonically bonded together using a wire, the bonding quality of
an ultrasonically-bonded portion of the wiring terminal and the
wire. The bonding quality inspection method of Patent Document 2 is
a method in which the bonding quality is inspected according to a
bonding waveform of a push-in amount, etc. of a bonding tool that
is acquired in the bonding apparatus (ultrasonic bonding
apparatus).
[0004] In Patent Document 3, there is disclosed an
ultrasonic-bonding control apparatus for determining, at the time a
bonding member and a bonding target member are bonded together by
the application of an ultrasonic wave using an ultrasonic bonding
apparatus, whether or not a crack failure or a bonding peel-off
trouble occurs in at least one of the bonding member and the
bonding target member. The ultrasonic-bonding control apparatus of
Patent Document 3 determines the bonded state of the bonding member
or the bonding target member on the basis of an output signal from
a vibration sensor abutting on the bonding target member or a
vibration sensor attached to a contactor for pressing the bonding
member.
CITATION LIST
Patent Document
[0005] Patent Document 1: Japanese Patent Application Laid-open No.
2012-83246 (Paragraphs 0016 to 0027; FIG. 3, FIG. 4) [0006] Patent
Document 2: International Application Publication No. WO2010/113250
(Paragraphs 0045 to 0058 and 0089; FIG. 1, FIG. 4, FIG. 5) [0007]
Patent Document 3: Japanese Patent Application Laid-open No.
2012-35299 (Paragraphs 0044, 0045, 0082 and 0083; FIG. 1, FIG.
8)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0008] According to the bonding inspection method of Patent
Document 1, because the ultrasonic wave is applied after completion
of the bonding, there is a problem that the time for applying the
ultrasonic wave arises, so that it takes time to manufacture a
semiconductor device. Further, according to the bonding inspection
method of Patent Document 1, there is a problem that, when, after
completion of the bonding an unevenness, a foreign substance or the
like exists on the surface of a portion to which the ultrasonic
wave is to be applied, the ultrasonic wave is not properly applied
thus making the detection data abnormal, so that the bonding
quality is, even though not problematic, erroneously determined to
be problematic.
[0009] In the bonding quality inspection method of Patent Document
2, the bonding quality is inspected according to the bonding
waveform of a push-in amount, etc. of the bonding tool that is
acquired in the bonding apparatus. However, in the ultrasonic
bonding, although an applied load and an amount of applied
displacement (push-in amount) are the main bonding parameters, even
when the amount of applied displacement is set to a certain value,
the actual amount of applied displacement may be different
therefrom depending on the rigidity of the bonding target member or
the bonding member. In addition, the bonding quality also varies
due to the influence of a foreign substance or an oxide film on the
interface in the bonded portion. Thus, according to the bonding
quality inspection method of Patent Document 2, there is a problem
that it is unable to precisely inspect the bonding quality
according only to the waveform acquired in the bonding apparatus
(ultrasonic bonding apparatus).
[0010] The ultrasonic-bonding control apparatus of Patent Document
3 is provided with the purpose of determining the bonded state
through detection of a vibration in such a manner that the
vibration sensor is attached to the bonding target member or to the
contactor for pressing the bonding member. However, it requires
causing the vibration sensor to abut on a product including the
bonding target member, or attaching the vibration sensor to the
contactor that is joined to a lead member for pressing the bonding
member, namely, to a vibration transmission member placed between
the lead member to which the ultrasonic horn is connected and the
bonding target member or the bonding member. Thus, there is a
problem that the productivity decreases.
[0011] The present invention has been made to solve the problems as
described above, and an object thereof is to provide an ultrasonic
bonding apparatus, an ultrasonic bonding inspection method and an
ultrasonically-bonded portion fabrication method, in which the
bonding quality of the bonding member ultrasonically bonded to the
bonding target member is precisely determined to be defective or
not in a short time.
Means for Solving the Problems
[0012] The ultrasonic bonding apparatus of the invention is an
ultrasonic bonding apparatus for bonding a bonding target member
and a bonding member together using an ultrasonic wave, and
comprises: an ultrasonic bonding machine having an ultrasonic tool
for applying the ultrasonic wave to the bonding target member
mounted on a fixed object fixed to a jig, while pressing the
bonding member against the bonding target member; and a bonding
inspection apparatus for inspecting a bonding quality of the
bonding target member and the bonding member. The bonding
inspection apparatus in the ultrasonic bonding apparatus is
characterized by comprising: a bonded-state measuring device for
detecting a vibration propagating in the jig or a housing of the
ultrasonic bonding machine equipped with the jig, using a sensor
that is fixed to the jig or the housing at a position at which it
does not make contact with the bonding target member and the
bonding member and that detects the vibration, to thereby output a
detection signal; and a bonded-state determination device for
determining, in a bonding process for the bonding target member and
the bonding member, a bonded state between the bonding target
member and the bonding member on the basis of the detection signal
outputted by the bonded-state measuring device.
Effect of the Invention
[0013] According to the ultrasonic bonding apparatus of the
invention, since it determines the bonded state between the bonding
target member and the bonding member on the basis of the detection
signal outputted by the bonded-state measuring device in the
bonding process, it is possible to inspect the bonding quality in
real-time in the bonding process, and to reduce time taken for the
quality inspection, and further to accurately determine whether the
quality is defective or not.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram showing an ultrasonic bonding apparatus
according to Embodiment 1 of the invention.
[0015] FIG. 2 is a block diagram of a bonded-state determination
device in FIG. 1.
[0016] FIG. 3 is a top view of a power semiconductor device in FIG.
1.
[0017] FIG. 4 is a side view of the power semiconductor device of
FIG. 3.
[0018] FIG. 5 is a cross-sectional view at a section along A-A of
the power semiconductor device of FIG. 3.
[0019] FIG. 6 is an enlarged cross-sectional view of a first
ultrasonically-bonded portion in FIG. 5.
[0020] FIG. 7 is an enlarged cross-sectional view of a second
ultrasonically-bonded portion in FIG. 5.
[0021] FIG. 8 is a diagram showing an example of an AE signal
waveform at the time bonding is non-defective.
[0022] FIG. 9 is a diagram showing an example of an AE signal
waveform at the time bonding is defective.
[0023] FIG. 10 is a flowchart showing a first example of a bonding
process according to Embodiment 1 of the invention.
[0024] FIG. 11 is a block diagram of another bonded-state
determination device in FIG. 1.
[0025] FIG. 12 is a diagram showing an example of an
arithmetically-processed waveform at the time bonding is
non-defective.
[0026] FIG. 13 is a diagram showing an example of an
arithmetically-processed waveform at the time bonding is
defective.
[0027] FIG. 14 is a diagram showing a first example of an
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1.
[0028] FIG. 15 is a diagram showing a second example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1.
[0029] FIG. 16 is a flowchart showing a second example of the
bonding process according to Embodiment 1 of the invention.
[0030] FIG. 17 is a diagram showing a third example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1.
[0031] FIG. 18 is a diagram showing a fourth example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1.
[0032] FIG. 19 is a flowchart showing a third example of the
bonding process according to Embodiment 1 of the invention.
[0033] FIG. 20 is a flowchart showing a fourth example of the
bonding process according to Embodiment 1 of the invention.
[0034] FIG. 21 is a flowchart showing a fifth example of the
bonding process according to Embodiment 1 of the invention.
[0035] FIG. 22 is a diagram showing a fifth example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1.
[0036] FIG. 23 is a diagram showing a bonded-state measuring device
according to Embodiment 2 of the invention.
[0037] FIG. 24 is a diagram showing another ultrasonic bonding
apparatus according to Embodiment 1 of the invention.
[0038] FIG. 25 is a diagram showing still another ultrasonic
bonding apparatus according to Embodiment 1 of the invention.
[0039] FIG. 26 is a diagram showing a wire bonding condition
employed in a wire bonding apparatus according to Embodiment 3 of
the invention.
[0040] FIG. 27 is a diagram for illustrating how to determine
whether bonding is defective or not, in an ultrasonic bonding
inspection method according to Embodiment 3 of the invention.
[0041] FIG. 28 is a diagram for illustrating a case where bonding
is determined to be non-defective by the ultrasonic bonding
inspection method according to Embodiment 3 of the invention.
[0042] FIG. 29 is a diagram for illustrating a case where bonding
is determined to be defective by the ultrasonic bonding inspection
method according to Embodiment 3 of the invention.
[0043] FIG. 30 is a diagram showing a hardware configuration
example for implementing function blocks of the bonded-state
determination device.
MODES FOR CARRYING OUT THE INVENTION
Embodiment 1
[0044] FIG. 1 is a diagram showing an ultrasonic bonding apparatus
according to Embodiment 1 of the invention, and FIG. 2 is a block
diagram of a bonded-state determination device in FIG. 1. FIG. 3 is
a top view of a power semiconductor device in FIG. 1, and FIG. 4 is
a side view of the power semiconductor device of FIG. 3. FIG. 5 is
a cross-sectional view at a section along A-A of the power
semiconductor device of FIG. 3. FIG. 6 is an enlarged
cross-sectional view of a first ultrasonically-bonded portion in
FIG. 5, and FIG. 7 is an enlarged cross-sectional view of a second
ultrasonically-bonded portion in FIG. 5. FIG. 8 is a diagram
showing an example of an AE signal waveform at the time bonding is
non-defective, and FIG. 9 is a diagram showing an example of an AE
signal waveform at the time bonding is defective. FIG. 10 is a
flowchart showing a first example of a bonding process according to
Embodiment 1 of the invention. FIG. 11 is a block diagram of
another bonded-state determination device in FIG. 1. FIG. 12 is a
diagram showing an example of an arithmetically-processed waveform
at the time bonding is non-defective, and FIG. 13 is a diagram
showing an example of an arithmetically-processed waveform at the
time bonding is defective. FIG. 14 is a diagram showing a first
example of an ultrasonic-wave application condition according to
the ultrasonic bonding apparatus of FIG. 1.
[0045] An ultrasonic bonding apparatus 50 includes an ultrasonic
bonding machine 20 for ultrasonically bonding a bonding member to a
bonding target member, and a bonding inspection apparatus for
inspecting a bonding quality of the bonding member ultrasonically
bonded to the bonding target member. The ultrasonic bonding machine
20 includes: a housing 28; a lower jig 24 for mounting thereon a
power semiconductor device 1 as a product; upper jigs 25 for fixing
the power semiconductor device 1 to the lower jig 24; an ultrasonic
oscillator 23 for oscillating an ultrasonic wave; an ultrasonic
horn 22 that is a resonator for efficiently transmitting the
ultrasonic wave oscillated by the ultrasonic oscillator 23 to an
ultrasonic tool 21; the ultrasonic tool 21 for actually applying
the ultrasonic wave to the bonding member and the bonding target
member; a movable stage 26 for moving the lower jig 24 in an
x-direction and a y-direction; an ultrasonic tool moving device 29
for moving the ultrasonic tool 21 in a Z-direction; and an
operation terminal 27 that is a control unit for controlling
respective instruments in the ultrasonic bonding machine 20. The
power semiconductor device 1 is an example of a fixed object fixed
to the jig (lower jig 24).
[0046] The bonding inspection apparatus 30 includes a bonded-state
measuring device 31 for measuring the bonded state of the bonding
member ultrasonically bonded to the bonding target member, and a
bonded-state determination device 32 for determining a bonding
quality of the bonding member and the bonding target member on the
basis of a detection signal sig1 containing the bonded state
measured by the bonded-state measuring device 31. The bonded-state
determination device 32 outputs a determination result signal sig2
to the operation terminal 27. The bonded-state measuring device 31
includes, for example: an AE sensor 33 for detecting as a sound (AE
(Acoustic Emission)) a vibration due to the ultrasonic wave
transmitted from the ultrasonic tool 21; a pre-amplifier 34 for
amplifying the signal of the AE sensor 33; and a measuring device
35 for measuring the signal amplified by the pre-amplifier 34. The
measuring device 35 outputs the signal detected by the AE sensor
33, as the detection signal sig1, to the bonded-state determination
device 32. Here, the acoustic emission (AE) is that which has a
high-frequency component of several kHz to several MHz and
propagates mainly in a material. The acoustic emission is suited
for use in detection of a high frequency signal that is likely to
be attenuated in air. The AE sensor is usually formed of a
piezoelectric element, such as PZT (lead zirconate titanate) or the
like.
[0047] The oscillation frequency of the ultrasonic oscillator 23
and the ultrasonic horn 22 is fixed. Note that the description has
been made citing the upper jigs 25 as an example for fixing the
power semiconductor device 1; however, the power semiconductor
device 1 may be fixed to the lower jig 24 using a screw hole and a
screw for attaching the power semiconductor device 1.
[0048] First, the power semiconductor device 1 subject to bonding
will be described. In the power semiconductor device 1, an IGBT
(Insulated Gate Bipolar Transistor) 12 as a power semiconductor
element 1 mounted on a circuit board 8, and an FwDi (Free-Wheeling
Diode) 13, are enclosed with a resin casing 2 by insert resin
molding and a cover 3. In the casing 2, attachment holes 7 for
attaching a heatsink (not shown) for dissipating heat during
operation are created. Further, upwardly from the upper surface of
the power semiconductor device 1, main terminals 4 and signal
terminals 5 are formed that are copper terminals for establishing
conduction to the outside. The inside of the casing 2 is sealed
with a silicone gel 19, and the upper side of the casing 2 is
covered with the cover 3. A bush 6 as a metal cylinder is fitted to
the inner surface of the attachment hole 7.
[0049] The circuit board 8 includes: a 0.32 mm-thick
Si.sub.3N.sub.4 ceramic plate 9 provided as an insulating material;
a 0.7 mm-thick copper wiring pattern 11 for heat dissipation formed
on a back surface of the ceramic plate 9; and 0.8 mm-thick copper
wiring patterns 10a, 10b, 10c and 10d that are formed on the upper
surface of the ceramic plate 9. For that wiring patterns, numeral
10 is used collectively, and numerals 10a, 10b, 10c, 10d are used
when they are to be described distinctively. To the wiring pattern
10, the IGBT 12 and the FwDi 13 are bonded using a solder 14. In
FIG. 5, an example is shown in which the IGBT 12 and the FwDi 13
are bonded to the wiring pattern 10b. The circuit board 8 and the
casing 2 are fixed to each other using an adhesive 16.
[0050] To the respective IGBT 12, FwDi 13 and wiring patterns 10,
multiple Al connecting wires 15a, 15b and 15c each having a
diameter of 200 to 400 .mu.m are connected by wire bonding using
ultrasonic bonding. For the connecting wires, numeral 15 is used
collectively, and numerals 15a, 15b, 15c are used when they are to
be described distinctively. In FIG. 5, an example is shown in which
the IGBT 12 and the FwDi 13 are connected to each other by the
connecting wire 15b, the wiring pattern 10a and the wiring pattern
10d are connected to each other by the connecting wire 15a, and the
wiring pattern 10b and the wiring pattern 10c are connected to each
other by the connecting wire 15c. Note that a gate as a control
electrode of the IGBT 12 and the wiring pattern 10d are connected
to each other by an unshown connecting wire 15. Further, the copper
terminals as the bonding members for establishing conduction to the
outside, namely, the main terminals 4 and the signal terminals 5,
are ultrasonically bonded to the wiring patterns 10 as the bonding
target members. The main terminals 4 and the signal terminals 5
each have a plate thickness of 0.8 mm, and the areas of
ultrasonically bonded portions 18, 17 connected to the wiring
patterns 10 are each provided as a region of 3 mm.times.5 mm. The
main terminals 4 are each a terminal through which a current flows
that is larger than that of the signal terminal 5, and are
connected to main electrodes of the power semiconductor element,
for example, an emitter and a collector that are main electrodes of
the IGBT 12. The plate thickness of the wiring patterns 10 is 0.2
to 1.5 mm, and a width of about 1 to 50 mm is generally applied for
them.
[0051] As shown in FIG. 7, the ultrasonically bonded portion 18
corresponds to a part of the main electrode 4 to be pressed by the
ultrasonic tool 21 and is a part between broken lines 52a and 52b.
As shown in FIG. 6, the ultrasonically bonded portion 17
corresponds to a part of the signal electrode 5 to be pressed by
the ultrasonic tool 21 and is a part between broken lines 51a and
51b.
[0052] Using the schematic diagram of FIG. 1, description will be
made about the ultrasonic bonding process for the signal terminals
5 as the bonding members and the wiring patterns 10 as the bonding
target members. First, using the upper jigs 25, the power
semiconductor device 1 is fixed to the lower jig 24 in the
ultrasonic bonding apparatus 50. Then, the ultrasonic tool 21 is
held against the signal electrode 5 and then, while it is being
pressed thereto, ultrasonic vibration is applied on that electrode
using the ultrasonic horn 22, so that an oxide film and a stain,
formed and adhered around the bonding interface are removed,
causing newly developed surfaces to tightly adhere together, to
thereby form a bonding layer. The frequency used in the ultrasonic
bonding is 10 to 40 kHz, and its amplitude to be applied is 10 to
50 .mu.m as single amplitude. Note that the load during pressing is
about several hundreds N, and thus the load is significantly larger
than that in the case of an Al wire (connecting wire 15) or an Al
tape (at the time of ribbon bonding) whose material strength and
size (in particular, its material thickness) are small. In
addition, after the bonding, the head of the ultrasonic tool 21 and
the signal terminal 5 are put into a state biting into each other,
so that their biting is designed to be eliminated in such a manner
that, at the time of moving up the ultrasonic tool 21, the
ultrasonic tool 21 is moved up while ultrasonic vibration is being
applied thereto, so as to allow smooth transition to the bonding of
the next signal terminal 5. An ultrasonic bonding condition may
include a load, an amount of displacement, energy, a bonding time
and the like, and such a condition has been specified beforehand so
that an adequate bonding quality will be achieved. Although there
is a case where such a condition is set to the same values
throughout the bonding, in some cases, the bonding condition is set
so that the load will be gradually increased during application of
the ultrasonic wave, as shown, for example, in FIG. 14. FIG. 14 is
an example of an ultrasonic-wave application condition, in which
ultrasonic-wave application energy 77 and an applied force 78 are
drawn simultaneously. In FIG. 14, the abscissa represents time, and
the ordinate represents the application energy or the applied
force. In FIG. 14, an example is shown in which the load is
increased until Time ta1, and then a constant load is applied until
bonding-finished Time te1 at which the bonding is finished.
[0053] The AE sensor 33 is attached to the lower jig 24 in the
ultrasonic bonding apparatus 50. The attaching method of the AE
sensor 33 desirably uses screw fastening or an adhesive. It is
desired that an insert material such as a gel or the like, that
allows a sound to pass through easily, be applied between a
detection portion of the AE sensor 33 and the lower jig 24.
[0054] A method for detecting an AE signal by way of the AE sensor
will be described. The AE sensor 33 is connected to the
pre-amplifier 34 through a cable, and a signal detected by the AE
sensor 33 is amplified by the pre-amplifier 34 and is, thereafter,
further amplified by the measuring device (main-amplifier) 35, and
is then outputted as the detection signal sig1. The detection
signal sig1 is a voltage analog signal. The detection signal sig1
is outputted to the bonded-state determination device 32, and the
bonded-state determination device 32 performs numerical arithmetic
processing on the voltage itself or voltage signal of the detection
signal sig1, to thereby determine whether the bonding quality of
the bonding member and the bonding target member is defective or
not. The bonded-state determination device 32 includes: a signal
input unit 36 for importing the detection signal sig1; a signal
processing unit 37 for performing signal processing on the
detection signal sig1; a determination unit 39 for determining
whether the bonding quality is defective or not; and a
determination result output unit 40 for outputting the
determination result signal sig2 containing resultant information
determined by the determination unit 39. The signal processing unit
37 performs numerical arithmetic processing on the voltage itself
or voltage signal of the detection signal sig1. The signal
processing unit 37 extracts, for example, a waveform resulting from
plotting a positive maximum voltage and a negative maximum voltage
at each time in the detection signal sig1, namely, a
circumferential shape in FIG. 8 or FIG. 9. It is desired that the
AE sensor 33 to be employed can measure a range of frequencies that
the ultrasonic horn 22 has.
[0055] The ultrasonic bonding apparatus 50 of Embodiment 1 is
characterized in that whether the bonding quality is defective or
not is determined by the detection of the AE signal at the time of
ultrasonic bonding, and that the inspection is performed by the AE
sensor 33 attached, not to the product or the ultrasonic horn 22,
but to the lower jig 24 of the ultrasonic bonding apparatus
(characteristic 1).
[0056] The AE signals measured by the bonded-state measuring device
31, namely, the detection signals sig1, are shown in FIG. 8 and
FIG. 9. FIG. 8 and FIG. 9 show examples of the AE signal waveform
at the time bonding is non-defective and at the time bonding is
defective, respectively. In FIG. 8 and FIG. 9, the ordinate
represents a voltage, and the abscissa represents time. In FIG. 8
and FIG. 9, the large voltage-amplitude zone corresponds to an AE
signal waveform in a state in which the ultrasonic wave is being
applied. An AE signal waveform 71 at the time bonding is
non-defective is almost constant during application of the
ultrasonic wave. In contrast, an AE signal waveform 72 at the time
bonding is defective is not constant during application of the
ultrasonic wave, and shows higher values at some several spots as
shown in a broken-line frame 73.
[0057] Using FIG. 10, the bonding process according to Embodiment 1
will be described. In Step S001, product introduction is done. An
intermediate product before connection with the main terminals 4
and the signal terminals 5 is introduced into the ultrasonic
bonding machine 20 of the ultrasonic bonding apparatus (product
introducing step). The intermediate product of the power
semiconductor device 1 to be introduced into the ultrasonic bonding
machine 20 is without the cover 3, the silicone gel 19, the main
terminals 4 and the signal terminals 5. Specifically, the
intermediate product of the power semiconductor device 1 is mounted
on the lower jig 24 and fixed the jig 24 using the upper jigs 25.
In Step S002, a first terminal, for example, the upper right signal
terminal 5 in FIG. 3, is subjected to ultrasonic bonding and the
detection signal sig1 is monitored by the bonded-state measuring
device 31 (detection signal monitoring step).
[0058] In Step S003, based on the detection signal sig1, the
bonded-state determination device 32 determines the bonded state
between the first terminal (signal terminal 5) as the bonding
member and the wiring pattern 10 as the bonding target member
(bonded-state determination step). When, in Step S003, the bonded
state is determined to be non-defective, the flow moves to Step
S004, whereas when the bonded state is determined to be defective
(bad), the flow terminates. In Step S004, the terminal bonding in
operation is stopped (ultrasonic-wave application stopping step),
and then the flow moves to Step S005. In Step S004, the application
of the ultrasonic wave in the bonding condition and the pressing of
the ultrasonic tool 21, for the terminal in operation, are stopped.
Specifically, the ultrasonic tool 21 is moved so as to be released
from the terminal in operation, for example, it is moved up. At the
time the ultrasonic tool 21 is moved up, application of an
ultrasonic wave in a releasing condition for eliminating the biting
with the terminal (signal terminal 5) is performed. The ultrasonic
wave in the releasing condition has energy lower than that of an
ultrasonic wave, for example, in the bonding condition.
[0059] In Step S005, it is determined whether or not bonding has
been completed for all terminals. When it is determined in Step
S005 that a terminal to be bonded as the bonding member still
remains, namely, bonding has not been completed, the flow returns
to Step S002, whereas when it is determined that the terminal to be
bonded does not remain, namely, bonding has been completed for all
terminals, the flow moves to Step S006. In the example shown in
FIG. 3, seven terminals are provided, so that Steps S002 to S005
are executed seven times. The seven terminals are the four signal
terminals 5 and the three main terminals 4. In Step S006, the
product is discharged (product discharging step), so that the flow
terminates. In Step S006, the upper jigs 25 are removed and the
intermediate product of the power semiconductor device 1 is
discharged from the ultrasonic bonding machine 20. When the bonding
process for the intermediate product of one power semiconductor
device 1 has been completed, the bonding process for an
intermediate product of the next power semiconductor device 1 is
executed.
[0060] The bonded-state determination device 32 performs the
bonded-state determination step on the basis of the detection
signal sig1 outputted by the bonded-state measuring device 31 in
the detection signal monitoring step. The bonded-state
determination device 32 imports the detection signal sig1 using the
signal input unit 36, and performs pre-processing before
determination on the detection signal sig1 provided in the
detection signal monitoring step, by executing signal processing on
the detection signal sig1, for example, by extracting the
circumferential shape, using the signal processing unit 37. The
determination unit 39 determines whether or not a high voltage
value emerges in the circumferential shape of the waveform of the
detection signal sig1 (detection waveform) as shown in the
broken-line frame 73 in FIG. 9. When a high voltage value emerges
in the circumferential shape of the waveform of the detection
signal sig1 as shown in the broken-line frame 73 in FIG. 9, namely,
when unusual information is detected that is not associated with a
reference waveform and that indicates emergence of a high voltage
value, or the like, the bonding is determined to be defective; and
when a high voltage value as shown in the broken-line frame 73 in
FIG. 9 does not emerge in the circumferential shape of the waveform
of the detection signal sig1, namely, when unusual information is
not detected that is not associated with the reference waveform and
that indicates emergence of a high voltage value, or the like, the
bonding is determined to be non-defective. The determination result
output unit 40 outputs the determination result signal sig2
containing resultant information indicative of the determination
result determined by the determination unit 39.
[0061] A waveform as a reference for the detection signal sig1
(waveform of a reference detection signal, or reference waveform)
that is to be used in the bonded-state determination step at the
time of determining whether the bonded state is defective or not,
is:
[0062] a waveform of the detection signal sig1 which was measured
beforehand by the bonded-state measuring device 31 when a bonding
process was executed beforehand in an ultrasonic bonding condition
for bonding the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5) together and
whereby a bonded state corresponding to the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) was determined to be non-defective; or
[0063] its pre-processed waveform obtained by the extraction of the
circumferential shape, or the like.
[0064] The AE signal waveform 71 at the time bonding is
non-defective, which was acquired when the bonding process was
executed beforehand, is the waveform of the reference detection
signal (reference waveform). The AE signal waveform 71 at the time
bonding is non-defective or the AE signal waveform 72 at the time
bonding is defective, which is detected at the time the bonded
state is determined to be defective or not, is a waveform of the
detection signal subject to determination in the bonded-state
determination step.
[0065] The reason why the characteristic 1 aforementioned is
employed will be described. According to the bonding inspection
method of Patent Document 1, since an AE signal is detected in the
atmosphere through an air layer from the bonded portion, a problem
resides in noise due to the intermediation of the air layer, even
if a soft material that easily allows signal transmission, such as
a silicone rubber, a resin sheet or the like, is placed on the head
of the AE sensor. Further, in a production site, a facility for use
in another process is also placed in the same room and thus, a
sound or vibration (environmental noise) occurs due to that
facility, so that such a sound or vibration will propagate in the
atmosphere to thereby create large noise for the AE signal to be
detected by the AE sensor. Thus, according to the bonding
inspection method of Patent Document 1, since the large noise is
superimposed on the AE signal, it is unusable in a usual production
site. Unlike the bonding inspection method of Patent Document 1,
according to the ultrasonic bonding apparatus 50 of Embodiment 1,
since the AE sensor 33 is attached onto the lower jig 24, there is
no such a sound or vibration intruding through an air layer toward
the detection surface of the AE sensor 33 and accordingly, the
noise that occurs by the bonding inspection method of Patent
Document 1 will not be detected by the AE sensor 33. Namely,
according to the ultrasonic bonding apparatus 50 of Embodiment 1,
since environmental noise is less likely to intrude, it is possible
to detect the AE signal, highly accurately.
[0066] In order to further reduce noise in the AE signal to the
minimum, it is effective to use the AE sensor 33 that can detect
the frequencies corresponding to the ultrasonic horn 22 and does
not detect frequencies where noise occurs, and thus that is usable
in a specific frequency range(s).
[0067] Further, the bonding inspection method of Patent Document 1
is a method in which the AE sensor is placed in proximity to a
semiconductor chip, to thereby detect the AE signal. When the
bonding inspection method of Patent Document 1 is used, many
problems to be solved arise as described below. With the use of
this method, there are cases where, when the AE sensor is used
repetitively, a foreign substance adheres to that AE sensor.
Further, if the AE sensor is attached in the product, a possibility
arises that the foreign substance falls down to thereby affect the
property. Further, when the AE signal is to be detected
individually in the products, attachment and detachment of the AE
sensor (translation of the AE sensor) are required for every
product, and this creates a problem that the inspection time
including time for the attachment and detachment becomes longer
than the ultrasonic bonding time. Furthermore, when the AE signal
is to be acquired while reducing noise as much as possible, since
the gap between the measuring object and the AE sensor is desired
to be small, the gap between the measuring object and the AE sensor
33 is generally filled with a gel or adhesive. However, when the
gel or adhesive adheres to the product, a possibility arises that
the product can not exert an intended property. Further, when the
AE signal is acquired in such a manner that the AE sensor is made
contact with the semiconductor chip (semiconductor element), there
is also a problem that the AE sensor and the semiconductor chip
cause friction at their interface due to the application energy
during ultrasonic bonding, and this friction becomes a noise
factor. According to the bonding inspection method of Patent
Document 1, such problems arise, so that the AE sensor is desired
to be attached at a place other than the product at which the
vibration during ultrasonic bonding is less influential than
otherwise. In particular, as shown in FIG. 1, it is desired to be
attached to the lower jig 24 on which the product is fixed and
which provides a position where higher signal-detection accuracy
can be achieved.
[0068] As a method for performing inspection without making contact
with the product, temperature measurement using thermography, like
that using an infrared camera shown in FIG. 3 in Patent Document 1,
is conceivable as a possibility. However, because of dealing with
large current, the power semiconductor device 1 is designed to
efficiently dissipate heat. Thus, heat at the ultrasonic bonding
will be dissipated during that bonding, so that the accuracy is
poor according to such temperature-based inspection. Further, the
terminal shape of the power semiconductor device 1 is generally
different for each terminal, so that an amount of dissipated heat
is different for each terminal. Accordingly, a temperature
difference depending on the terminal shape becomes larger than the
difference depending on the bonding quality, and thus such
temperature-based inspection is not adequate also in this
viewpoint. Furthermore, the inside of the power semiconductor
device 1 is surrounded by the casing 2 and in that inside, the
wiring patterns 10 and the connecting wires 15 are complexly
connected to the terminals, so that heat is easily dissipated. For
this reason, there is also a problem that it is difficult to
confirm the temperature of the terminal bonded portion
(ultrasonically bonded portion 17, 18) directly by a
thermo-viewer.
[0069] Further, regarding the position at which the AE sensor is to
be attached, if it is outside the product (power semiconductor
device 1), the ultrasonic tool 21 may also be nominated therefor.
However, when the AE sensor 33 is attached onto the ultrasonic tool
21, a state of vibration caused by oscillation from the ultrasonic
horn 22 varies by the self-weight of the AE sensor 33, so that
attenuation occurs due to the self weight of the AE sensor 33, for
example. Thus, this is not appropriate. Furthermore, at the
ultrasonic bonding of the terminal (main terminal 4, signal
terminal 5), a very large amplitude is given to the terminal, and
thus there is also a problem that the attached AE sensor 33 may be
removed.
[0070] Further, with respect, in particular, to the case where a
fixed state between the terminal (main terminal 4, signal terminal
5) and the wiring pattern 10 is to be detected, in the AE signal by
the AE sensor 33 placed on the ultrasonic tool 21, a signal
component mainly from the ultrasonic horn 22 becomes large, so that
a signal component from the ultrasonically bonded portion 17, 18
becomes relatively small. For the detection of the signal component
from the ultrasonically bonded portion 17, 18, when the AE signal
by the AE sensor 33 placed on the fixing jig (lower jig 24) is
detected, higher accuracy will be provided.
[0071] It is noted that the material of the jig 24 is desired to
easily allow transmission of the AE signal, not to deform by the
load during ultrasonic bonding, and to be less thermally
deteriorated during the bonding. When a resin or ceramic material
is used, there is a problem that the signal may be attenuated due
to deterioration caused by the pressing force or the distance from
an AE-signal acoustic source to the AE sensor 33. As the material
of the lower jig 24, it is desired not to use a resin material,
etc. but to use a metallic material such as stainless steel,
aluminum alloy, or the like. The material of the lower jig 24 may
also be defined using a sound velocity. Namely, a material by which
a sound velocity of the ultrasonic wave propagating in the lower
jig 24 is 3000 m/s or more, transmits the AE signal more easily,
and is thus suited as the material of the lower jig 24.
[0072] The ultrasonic bonding apparatus 50 of Embodiment 1 inspects
non-destructively the bonded state between the bonding target
member (wiring pattern 10) and the bonding member (main terminal 4,
signal terminal 5), and thus has a feature capable of making the
inspection time shorter than that in the case where sampled
products are destructively inspected. Further, after completion of
the bonding, the application of an ultrasonic wave only for
inspecting whether bonding is defective or not, as in the bonding
inspection method of Patent Document 1, is unnecessary, so that the
ultrasonic bonding apparatus 50 of Embodiment 1 has a feature in
that such an additional time required for inspecting the bonded
state does not arise. Further, according to the ultrasonic bonding
apparatus 50 of Embodiment 1, because the AE signal at the time of
ultrasonic bonding is detected, it is possible not to be affected
by a variation at the time of application of the ultrasonic wave
for inspection (unevenness of an ultrasonic-wave applied portion, a
foreign substance, abrasion or cracking of the ultrasonic tool, or
the like) that is problematic in the bonding inspection method of
Patent Document 1.
[0073] Furthermore, according to the ultrasonic bonding apparatus
50 of Embodiment 1, whether the bonding is defective or not can be
determined in the bonding process, so that, if a bonding defect
should occur at a certain bonding spot, namely, if the bonded state
should be determined to be defective in the bonded-state
determination step, it is allowed to perform abandonment, or
repairing of the bonding defect to be described later. Thus,
according to the ultrasonic bonding apparatus 50 of Embodiment 1,
such a situation can be prevented where, despite a defective
product, the manufacturing process proceeds to the next or
following step making it unable to perform repairing of the bonding
defect; and thus unnecessary manufacturing time that would have
continued accordingly can be eliminated. As the result, it is
possible to prevent unnecessary cost from being generated. In the
case of incomplete bonding, when the defect is, for example, due to
lack of bonded area, repairing of the bonding defect is done by an
additional pressing and ultrasonic wave application, or the
like.
[0074] Further, the ultrasonic bonding apparatus 50 of Embodiment 1
can store the number of bonding members with which the bonded state
is determined to be defective, namely, defect-inspected number, to
thereby recognize the state of the ultrasonic bonding apparatus 50
by using the defect-inspected number. For example, when
defect-inspected numbers are sorted by number of products, date
manufactured or the like, it is possible, after confirming the
transition of the defect-inspected number, to take maintenance of
the apparatus when the defect-inspected number exceeds a preset
determination value. This also leads to preventing occurrence of
the bonding defect.
[0075] According to the ultrasonic bonding apparatus 50 of
Embodiment 1, when a silicone rubber layer that does not easily
allow transmission of the AE signal is provided under the lower jig
24 (between the lower jig 24 and the movable stage 26) or/and under
the facility (between the ultrasonic bonding machine 20 and the
floor on which that machine is placed), it is possible to further
reduce noise generated from the other facility in the room in which
the ultrasonic bonding machine 50 is placed, thus making it
possible to detect whether bonding is defective or not, more highly
accurately.
[0076] Furthermore, when a detection signal sig1 containing a value
at a specific frequency is generated through numerical arithmetic
processing, for example, an FFT (Fast Fourier Transform), on the AE
signals detected by the bonded-state measuring device 31, namely,
on the AE signal waveform 71, 72, it is possible to perform
high-level determination as to whether the bonded state is
defective or not, in the bonded-state determination device 32. FIG.
11 shows a bonded-state determination device 32 that performs
numerical arithmetic processing on the AE signals detected by the
bonded-state measuring device 31, namely, on the AE signal waveform
71, 72. The bonded-state determination device 32 of FIG. 11 results
from adding an arithmetic processing unit 38 to the configuration
of the bonded-state determination device 32 of FIG. 2. The
operations of the signal input unit 36, the signal processing unit
37 and the determination result output unit 40 in this bonded-state
determination device 32 are similar to those in the bonded-state
determination device 32 of FIG. 2. The arithmetic processing unit
38 performs numerical arithmetic processing, such as FFT or the
like, on a signal processed by the signal processing unit 37 from
the detection signal sig1. The operation of the determination unit
39 will be described later.
[0077] FIG. 12 shows an example of an arithmetically-processed
waveform at the time bonding is non-defective, which is an
arithmetically-processed waveform obtained through numerical
arithmetic processing from the AE signal waveform at the time
bonding is non-defective in FIG. 8. FIG. 13 shows an example of an
arithmetically-processed waveform at the time bonding is defective,
which is an arithmetically-processed waveform obtained through
numerical arithmetic processing from the AE signal waveform at the
time bonding is defective in FIG. 9. In FIG. 12 and FIG. 13, the
ordinate represents a voltage, and the abscissa represents a
frequency.
[0078] As shown in FIG. 12, in an arithmetically-processed waveform
74 at the time bonding is non-defective, respective components at a
frequency f1 that is the same as a frequency of the ultrasonic horn
22, at a frequency f2 that is twice said frequency, and at a
frequency f3 that is triple said frequency, are found. In contrast,
as shown in FIG. 13, in an arithmetically-processed waveform 75 at
the time bonding is defective, in addition to the components at the
frequency f1 that is the same as the frequency of the ultrasonic
horn 22 and at the frequencies that are natural number times said
frequency, other frequency components are found. The other
frequency components are components indicated in broken-line
circles 76a, 76b. These frequency components, that are found at
frequencies other than the frequency of the ultrasonic horn 22 and
the frequencies that are natural number times said frequency, are
frequency components of AE signals generated, for example, when the
back surface of the product (power semiconductor device 1) and the
jig (lower jig 24, upper jig 25) cause friction with each other in
a situation where fixing of the product to the jig is loosened by
the vibration at the time of ultrasonic bonding, or fixing of the
product to the jig is loosened in a case where the product has a
large warpage or a case like that. Namely, when the voltage value
of AE signal that has been found in a frequency band other than the
frequency of the ultrasonic horn 22 and the frequencies that are
natural number times said frequency, is converted into a numerical
value, and a threshold value therefor is set, it is possible to
determine whether defective or not (first determination on
arithmetically processed waveform). As the threshold value, such a
numerical value is set by which, when a waveform obtained through
numerical arithmetic processing from the waveform of the reference
detection signal previously described (arithmetically-processed
reference waveform) and the arithmetically-processed waveform
subject to the determination are compared with each other, unusual
information not found in the arithmetically-processed reference
waveform can be detected.
[0079] Further, a second determination on arithmetically processed
waveform may be performed that is different from the first
determination on arithmetically processed waveform. As compared
with the arithmetically-processed waveform 74 at the time bonding
is non-defective, in the arithmetically-processed waveform 75 at
the time bonding is defective, differences emerge in the voltage
values of AE signal that are found at the frequency that is the
same as the frequency of the ultrasonic horn 22 and the frequencies
that are natural number times said frequency. For example, when
fixing of the product to the jig is loose, the AE signal will be
that in which an AE signal generated at the time the back surface
of the product and the jig cause friction with each other, is
superimposed. When the fixing is loose, the voltage values of AE
signal found at the frequency that is the same as the frequency of
the ultrasonic horn 22 and the frequencies that are natural number
times said frequency, become lower. Namely, when the voltage values
of AE signal that have been found in frequency bands matching with
the frequency of the ultrasonic horn 22 and the frequencies that
are natural number times said frequency, are converted into
numerical values, and a threshold value therefor is set, it is
possible to determine whether defective or not. As the threshold
value, such a numerical value is set by which, when the waveform
obtained through numerical arithmetic processing from the waveform
of the reference detection signal previously described
(arithmetically-processed reference waveform) and the
arithmetically-processed waveform subject to the determination are
compared with each other, unusual information not found in the
arithmetically-processed reference waveform can be detected.
[0080] In the case of performing the second determination on
arithmetically processed waveform, the determination may be
performed only based on an AE signal detected in a frequency band
matching with the frequency of the ultrasonic horn 22. When the
determination is performed only based on the AE signal detected in
a frequency band where the voltage-value deference between when the
bonding is non-defective and when the bonding is defective is
largest, it is possible to adequately determine whether defective
or not. Because the voltage value of AE signal detected in a
frequency band matching with the frequency f1 of the ultrasonic
horn 22 will vary most significantly, even when the determination
is performed only based on the AE signal detected in that frequency
band, it is possible to adequately determine whether defective or
not.
[0081] In the first determination on arithmetically processed
waveform and the second determination on arithmetically processed
waveform, since their respective threshold values for
distinguishing between defectiveness and non-defectiveness of the
bonded state, are each set with reference to the waveform obtained
through numerical arithmetic processing from the waveform of the
reference detection signal previously described. Thus, the
numerical arithmetic waveform obtained through numerical arithmetic
processing from the waveform of the reference detection signal can
also be said to be a numerical arithmetically-processed waveform as
a reference for the detection signal sig1 (arithmetically-processed
reference waveform) to be used when the first determination on
arithmetically processed waveform or second determination on
arithmetically processed waveform is performed. The
arithmetically-processed waveform 74 which is a waveform obtained
through numerical arithmetic processing from the AE signal waveform
71 at the time bonding is non-defective that was acquired when a
bonding process was executed beforehand, is the
arithmetically-processed reference waveform. The
arithmetically-processed waveform 74 obtained through numerical
arithmetic processing from the AE signal waveform 71 at the time
bonding is non-defective or the arithmetically-processed waveform
75 obtained through numerical arithmetic processing from the AE
signal waveform 72 at the time bonding is defective, that is
detected at the time of determining whether the bonded state is
defective or not, is an arithmetically-processed waveform subject
to the determination in the bonded-state determination step.
[0082] In the case where the bonded-state determination step is
executed using the arithmetically-processed waveforms 74, 75, the
bonded-state determination device 32 operates as follows. The
bonded-state determination device 32 determines the bonded state
between the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5) on the basis
of:
[0083] the arithmetically-processed reference waveform
(previously-measured arithmetically-processed waveform 74) obtained
through numerical arithmetic processing from the waveform of the
reference detection signal which was measured beforehand by the
bonded-state measuring device 31 (previously-measured AE signal
waveform 71) when a bonding process was executed beforehand in an
ultrasonic bonding condition for bonding the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) together and whereby a bonded state corresponding to
the bonding target member (wiring pattern 10) and the bonding
member (main terminal 4, signal terminal 5) was determined to be
non-defective; and
[0084] the arithmetically-processed waveform (current
arithmetically-processed waveform 74, 75) obtained through
numerical arithmetic processing from the waveform of the detection
signal sig1 (current AE signal waveform 71, 72) measured by the
bonded-state measuring device 31 in the bonding process.
[0085] According to the ultrasonic bonding apparatus 50 of
Embodiment 1, by applying FFT analysis in the bonded-state
determination device 32 on the detected AE signals, it is possible
to differentiate an AE signal based on the bonded portion and an AE
signal due to weakly fixed product, and thus, in addition to
determining whether the bonded state between the bonding member and
the bonding target member is defective or not, it is possible to
recognize the reason therefor. Note that plural factors are assumed
to cause loosening of the product fixed to the jig and, for
example, such a case is conceivable where, when the product is
fixed using a screw, a gap due to the influence of warpage of the
product emerges beneath the screw fixing portion and between the
product and the lower jig 24, so that the screw is loosened by the
vibration during ultrasonic bonding.
[0086] In order to differentiate the fixing-related AE signal and
the bonding-related AE signal, such a method is useful in which
they are differentiated based on a frequency difference. As such a
frequency-based differentiation method, there is a method of
performing FFT analysis on a signal waveform measured using a
single AE sensor 33 to thereby differentiate the frequency
components, or a method of using multiple AE sensors 33 which are
each high in detection accuracy at a specific frequency to thereby
differentiate the signals detected by the respective AE sensors 33
according to their magnitudes.
[0087] The bonding condition for the bonding target member and the
bonding member may be other than the ultrasonic-wave application
condition shown in FIG. 14. For example, as shown in FIG. 15, the
bonding condition for the terminal (main terminal 4, signal
terminal 5) may be set to have steps. FIG. 15 is a diagram showing
a second example of the ultrasonic-wave application condition
according to the ultrasonic bonding apparatus of FIG. 1. In FIG.
15, the abscissa represents time, and the ordinate represents the
application energy or the applied force. In FIG. 15,
ultrasonic-wave application energy 77 and an applied force 79 are
drawn simultaneously. In FIG. 15, an example is shown in which a
weak load is applied until Time t1 and thereafter, the load is
gradually increased until Time ta1, and then a constant load is
applied until bonding-finished Time te1 at which the bonding is
finished. When the bonding condition for the terminal (main
terminal 4, signal terminal 5) is set to have the steps, and
inspection is performed on the AE signals obtained in an initial
period of ultrasonic-wave application until Time t1 in which the
ultrasonic wave is applied with the weak load that does not promote
the bonding, a following effect will be exerted. It is possible to
detect friction between the bonding member (main terminal 4, signal
terminal 5) and the bonding target member (wiring pattern 10) from
the AE signals just before the initiation of bonding, namely, the
AE signals obtained until Time t1, so that a surface state
(unevenness, a foreign substance) at the bonding interface,
abrasion or cracking of the ultrasonic tool 21, and the like, can
be inspected before the bonding.
[0088] Further, the inspection result, namely, the determination
result of the bonded state, may also be fed back to the ultrasonic
bonding apparatus 50. Feeding back the determination result of the
bonded state to the ultrasonic bonding apparatus 50 makes it
possible to increase the bonding time when, for example, the bonded
area has not reached its target, to decrease the bonding time when
the bonded area has reached the target, and to properly adjust the
bonding condition according to the determination result of the
bonded state. Accordingly, a constant bonding quality can be
achieved. Furthermore, when bonding processing is stopped just
after the bonding is completed, unnecessary energy is eliminated
from being applied to the product. This suppresses the heat during
bonding from traveling through the copper wiring pattern 10 or/and
the terminal (main terminal 4, signal terminal 5) to cause thermal
damage to a member therearound, in the case of ultrasonic bonding
in which large load is applied. Further, this suppresses the
damage, etc. of the wiring pattern 10 and the terminal (main
terminal 4, signal terminal 5).
[0089] FIG. 16 is a flowchart showing a second example of the
bonding process according to Embodiment 1 of the invention. FIG. 17
is a diagram showing a third example of the ultrasonic-wave
application condition according to the ultrasonic bonding apparatus
of FIG. 1. FIG. 18 is a diagram showing a fourth example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1. The flowchart shown in FIG. 16 is an
example resulting from adding Steps S007 and S008 to the flowchart
of FIG. 10 so that the determination result of the bonded state is
fed back. Description will be made about portions other than those
in the flowchart of FIG. 10.
[0090] The bonded-state determination step as Step S003 is executed
at plural timings given between a time earlier than a planned
bonding-finished time and a maximum time up to which the condition
is changeable. Note that there are also cases where the bonded
state is determined to be non-defective at the first timing of
executing the determination.
[0091] In Step S003, based on the detection signal sig1, the
bonded-state determination device 32 determines the bonded state
between the first terminal (signal terminal 5) as the bonding
member and the wiring pattern 10 as the bonding target member
(bonded-state determination step). When, in Step S003, the bonded
state is determined to be non-defective, the flow moves to Step
S004. When, in Step S003, the bonded state is determined to be
defective (bad), the flow moves to Step S007. In Step S007, whether
the condition is changeable or not is determined (bonding condition
determination step), and when it is determined to be changeable,
the bonding condition is changed in Step S008 (bonding condition
changing step), and then the flow returns to Step S002. When the
condition is determined to be not changeable in Step S007, the flow
terminates (defective bonding terminating step). Note that when the
bonding condition changing step as Step S008 has been executed, the
detection signal monitoring step as Step S002 and the bonded-state
determination step as Step S003 to be executed in the ultrasonic
bonding condition changed in the bonding condition changing step,
correspond to a bonding continuing step. The ultrasonic-wave
application stopping step as Step S004 is also a non-defective
bonding stopping step in which, when the bonded state between the
bonding target member (wiring pattern 10) and the bonding member
(main terminal 4, signal terminal 5) is determined to be
non-defective in the bonded-state determination step as Step S003,
the bonding process in operation for the bonding target member and
the bonding member is stopped.
[0092] Description will be made about a case where the bonding
condition to be changed is a bonding time, for example. In Step
S007, it is determined whether the maximum time up to which the
condition is changeable is reached or not. Specifically, if the
maximum time is not reached, the condition is determined to be
changeable, whereas if the maximum time is reached, the condition
is determined to be not changeable. FIG. 17 is an example in which
the bonding time is extended up to a time later than the planned
bonding-finished time, and FIG. 18 is an example in which the
bonding is finished at a time earlier than the planned
bonding-finished time. In FIG. 17 and FIG. 18, the abscissa
represents time, and the ordinate represents the application energy
or the applied force. In FIG. 17 and FIG. 18, ultrasonic-wave
application energy 77 and an applied force 78 are drawn
simultaneously. Time te1 represents the planned bonding-finished
time. Time te1a represents a bonding-finished time after extension,
and Time te1b represents a bonding-finished time after shortening.
As shown in FIG. 18, when the flow moves to Step S004 at a time
earlier than the planned bonding-finished time (Time te1), the
bonding time becomes shorter, and as shown in FIG. 17, when the
flow moves to Step S004 at a time later than the planned
bonding-finished time (Time te1), the bonding time becomes longer.
In this manner, according to the ultrasonic bonding apparatus 50 of
Embodiment 1 in which the determination result of the bonded state
is fed back, the bonding condition can be adjusted properly.
[0093] When the ultrasonic wave is continued to be applied after
completion of the bonding, such a case may arise where a foreign
substance is produced due to abrasion between the terminal (main
terminal 4, signal terminal 5) and the ultrasonic tool 21. However,
adjusting the bonding condition properly according to the
determination result of the bonded state, namely, stopping the
application of the ultrasonic wave promptly when the bonded state
is determined to be non-defective, makes it also possible to
prevent the production of the foreign substance. Furthermore, this
also leads to reducing the deterioration of the ultrasonic tool 21
caused by abrasion, to thereby make the ultrasonic tool 21 longer
in duration of life. Heretofore, if even only one of the plural
terminals in the power semiconductor device 1 is lack of bonded
area, it is required to determine the device to be defective or to
perform repairing after completion of inspection for all of the
terminals. However, according to the ultrasonic bonding apparatus
50 of Embodiment 1, feeding back the determination result of the
bonded state in the above manner in the ultrasonic bonding process,
makes it possible to almost eliminate the defect due to lack of
bonded area. The adjustment of the bonding condition using feedback
to the ultrasonic bonding apparatus 50 is a particular advantage
that is achievable only when the inspection is performed during
ultrasonic bonding.
[0094] Since the power semiconductor device 1 is larger in size in
comparison with a general semiconductor device, its warpage as a
product is relatively large in comparison with the general
semiconductor device. The force for fixing the product at the time
of ultrasonic bonding is generally controlled to have a given
constant value. However, for example, when the warpage of the
product is large, such a case may arise in which the product is
vibrated during the bonding, so that the energy for ultrasonic
bonding is not properly applied to the ultrasonically bonded
portion 17, 18. This vibration of the product can be detected using
the AE signal. FIG. 19 is a flowchart showing a third example of
the bonding process according to Embodiment 1 of the invention. The
flowchart shown in FIG. 19 is an example resulting from adding Step
S010 to the flowchart of FIG. 10 so that the vibration of the
product is detected and its resultant is fed back to the ultrasonic
bonding apparatus 50.
[0095] In Step S010, immediately after the initiation of the
ultrasonic bonding, a vibration of the product is detected using
the AE signal, so that the fixed state of the product is confirmed
(product fixed-state confirming step). When, in Step S010, the
fixed state of the product is non-defective, the flow moves to Step
S003. When, in Step S010, the fixed state of the product is
defective, the flow is interrupted tentatively and the force for
fixing the product is increased. At the time of restart, processing
is carried out from Step S002. As a method of increasing the force
for fixing, when the product is to be fixed by screw fastening, a
method of increasing a screw fastening torque is useful. Further,
when it is to be fixed using the upper jigs 25, in order to
increase clamping power of the upper jigs 25, a method of enhancing
the pressure thereto is useful.
[0096] According to the ultrasonic bonding apparatus 50 of
Embodiment 1 in which the bonding process shown by the flowchart of
FIG. 19 is executed, it is possible, immediately after the
initiation of the bonding, to increase the force for fixing the
product upon confirmation of the fixed state of the product, to
thereby perform the bonding normally. Note that Step S010 may be
added in between Step S002 and Step S003 in the flowchart of FIG.
16. Even in this case, it is possible to increase the force for
fixing the product immediately after the initiation of the bonding,
to thereby perform the bonding normally.
[0097] In order that the bonding quality may not be affected by
individual differences between the products, a following method is
also provided. The fixed state of the product may be detected
before the bonding in such a manner that, before the ultrasonic
bonding, the ultrasonic tool 21 is oscillated while being pushed
against a region on the wiring pattern 10 that is functionally
unnecessary for the product, and the AE signal at that time is
detected. FIG. 20 is a flowchart showing a fourth example of the
bonding process according to Embodiment 1 of the invention. The
flowchart shown in FIG. 20 is an example resulting from adding Step
S011 to the flowchart of FIG. 10 so that the vibration of the
product is detected and its resultant is fed back to the ultrasonic
bonding apparatus 50. In Step S011, operations similar to those in
Step S010 in the flowchart of FIG. 19 are carried out.
[0098] In Step S011, before the ultrasonic bonding, the vibration
of the product is detected using the AE signal, so that the fixed
state of the product is confirmed (product fixed-state confirming
step). When, in Step S011, the fixed state of the product is
non-defective, the flow moves to Step S002. When, in Step S011, the
fixed state of the product is defective, the flow is interrupted
tentatively and the force for fixing the product is increased. At
the time of restart, processing is carried out from Step S011. The
method of increasing the force for fixing the product is the same
as the method described with respect to the flowchart of FIG. 19.
According to the ultrasonic bonding apparatus 50 of Embodiment 1 in
which the bonding process shown by the flowchart of FIG. 20 is
executed, it is possible to confirm the fixed state of the product
before the bonding, to thereby adjust the force for fixing the
product before the bonding. This makes it possible to achieve the
products with uniform bonding quality.
[0099] Furthermore, when the above method of pushing the ultrasonic
tool 21 to detect the vibration beforehand, is performed at
multiple points on the wiring pattern 10 in a common product, the
accuracy can be enhanced. In particular, when the method is
performed near the four corners of the circuit board 8 each
provided as a product fixing portion, it is possible to immediately
determine which fixing portion(s) among four fixing portions in the
case 2 (its portions where the attachment holes 7 are created)
should be adjusted, and the accuracy can be further enhanced. By
such a way, the fixed state of the product can be determined before
the initiation of the ultrasonic bonding, so that the ultrasonic
bonding can be performed with the force for fixing the product
increased before the ultrasonic bonding. It is possible to decrease
the rate of cases where the bonding is determined to be defective
in the bonded-state determination step as Step S003. Further, when,
in Step S011, the fixed state of the product is defective, it is
allowed that the processing is once terminated and then, after the
force for fixing the product is increased, the product of the same
is introduced again into the bonding process (put into execution
from START).
[0100] It is noted that Step S011 may be added in between Step S001
and Step S002 in the flowchart of FIG. 16.
[0101] Even in this case, it is possible to confirm the fixed state
of the product before the bonding, to thereby adjust the force for
fixing before the bonding. This makes it possible to achieve the
products with uniform bonding quality.
[0102] So far, the description has been made about the case of
using the AE signal during application of the ultrasonic wave at
the bonding in the ultrasonic bonding process. However, as
described previously, in some instances, an ultrasonic wave is
applied to the ultrasonic tool 21 at the time it is to be released
(tool releasing time), in order to eliminate biting between the
ultrasonic tool 21 and the terminal after completion of the
bonding, so that a determination result using the AE signal due to
application of the ultrasonic wave at the tool releasing time, may
be fed back to the ultrasonic bonding apparatus 50. FIG. 21 is a
flowchart showing a fifth example of the bonding process according
to Embodiment 1 of the invention. The flowchart shown in FIG. 21 is
an example resulting from adding Step S012 to the flowchart of FIG.
10 so that the bonded state is determined and its resultant is fed
back to the ultrasonic bonding apparatus 50. Description will be
made about portions other than those in the flowchart of FIG.
10.
[0103] In Step S004, the application of the ultrasonic wave and the
pressing of the ultrasonic tool 21 for the terminal in operation
are stopped. Thereafter, in Step S012, an ultrasonic wave is
applied in order to eliminate biting between the ultrasonic tool 21
and the terminal after completion of the bonding. In the fifth
example of the bonding process, the application of the ultrasonic
wave in the releasing condition and the releasing of the ultrasonic
tool that are employed in Step S004 in the first to fourth examples
of the bonding process, are performed in Step S012. Then, during
application of the ultrasonic wave in the releasing condition, the
detection signal sig1 is monitored by the bonded-state measuring
device 31 (post-stopping detection signal monitoring step). The
bonded-state determination device 32 imports the detection signal
sig1 using the signal input unit 36, and performs signal processing
on the detection signal sig1, for example, performs extraction of
the circumferential shape, using the signal processing unit 37, so
that monitoring of the detection signal sig1 in the detection
signal monitoring step is done.
[0104] Using a low voltage value indicative of non-defectiveness in
bonding, the determination unit 39 determines whether or not, in
the circumferential shape of the detection signal sig1, a shape
which is like that shown in the broken-line frame 73 in FIG. 9 (low
quality shape), or the like, emerges. When the low quality shape or
the like emerges in the circumferential shape of the detection
signal sig1, the bonding condition is determined to be improper, so
that changing of the bonding condition (updating of bonding
condition) is performed. When the low quality shape or the like
does not emerge in the circumferential shape of the detection
signal sig1, the bonding condition is determined to be proper, so
that changing of the bonding condition (updating of bonding
condition) is not performed, namely, the current bonding condition
is maintained. Step S012 is a bonding-condition determination and
bonding-condition updating step.
[0105] In the case where the inspection is performed according to
this method, it is possible to predict from, for example, an AE
signal of the previous terminal after being bonded ultrasonically,
a bonding quality at the time ultrasonic bonding is performed in
the same condition. This makes it possible, when degradation in the
bonding quality of the next terminal is predicted from the AE
signal of the previous terminal, to suppress the degradation in the
bonding quality by changing the condition for the next terminal.
For example, in the case where the previous terminal has been
degraded in the bonded state after the bonding, feedback is
performed for changing the bonding condition, such as, for making
higher the bonding load (applied force) for the next terminal as
shown in FIG. 22 or for increasing the ultrasonic-wave application
time, so that the degradation in the bonding quality can be
prevented and thus the bonding quality is maintained.
[0106] FIG. 22 is a diagram showing a fifth example of the
ultrasonic-wave application condition according to the ultrasonic
bonding apparatus of FIG. 1. In FIG. 22, the abscissa represents
time, and the ordinate represents the application energy or the
applied force. In FIG. 22, ultrasonic-wave application energy 77
and applied forces 78, 78a are drawn simultaneously. The magnitude
of the applied force 78a (load) is higher than the magnitude of the
applied force 78 (load). Note that such a bonding-condition
determination may be performed using an arithmetically processed
waveform obtained through numerical arithmetic processing, such as,
FFT or the like. Further, Step S012 may be added in between Step
S004 and Step S005 in the flowchart of FIG. 16. Even in this case,
when degradation in the bonding quality of the next terminal is
predicted from the AE signal of the previous terminal, it is
possible to suppress the degradation in the bonding quality by
changing the following condition.
[0107] Inspection of the bonded state, etc. may also be performed
using multiple AE sensors 33. When the inspection is performed
using the multiple AE sensors 33, a following effect will be
exerted. In the case where the multiple AE sensors 33 have their
respective detection frequency ranges with peaks different from
each other, it is possible, without performing FFT analysis, to
detect a frequency band of the generated signals by comparing the
magnitudes of the signals detected by the individual AE sensors 33
relatively with each other. This makes it easier to differentiate
the generation sources of the signals.
[0108] In the case where the multiple AE sensors 33 have their
respective detection frequency ranges with peaks equal or
equivalent to each other, it is possible to specify or narrow down
to, a loosened fixing spot among product fixing spots existing
plurally, by making confirmation on the signals detected by the
respective AE sensors 33 while finely partitioning a period of
generation time of these signals. Namely, since the transmission of
the AE signal in the lower jig 24 takes time, it is possible to
determine that a fixing portion near the AE sensor 33 that has
detected the signal most quickly is loosened.
[0109] In the case of differentiating the generation sources
according to the differences in the detection frequency ranges, the
fixed positions of the multiple AE sensors 33 may be any positions
if they are on the lower jig 24. In order to specify a
fixing-loosened spot according to the generation time, it is
desired to place the AE sensors 33 at equal intervals or in a
regular manner. For example, when the four corners of the product
are fixed by screws, it is possible to achieve such detection by
placing the respective AE sensors 33 near the screws.
[0110] So far, the description has been made about the case of the
ultrasonic bonding process for the copper terminal (main terminal
4, signal terminal 5); however, in a wire bonding process that is a
process in which an ultrasonic wave is applied similarly, namely,
in an ultrasonic bonding process using the connecting wire 15 as a
bonding member, an effect similar to the above will also be
exerted. Further, with a structure that is different to that of the
power semiconductor device 1 shown in this embodiment, if it is a
structure to be bonded ultrasonically, an effect similar to the
above will also be exerted. In this embodiment, the description has
been made about the case of ultrasonic bonding between metals;
however, in the case where a material other than metal is bonded or
adhesively joined, an effect similar to the above will also be
exerted.
[0111] As described above, the ultrasonic bonding apparatus 50 of
Embodiment 1 is an ultrasonic bonding apparatus for bonding a
bonding target member (wiring pattern 10) and a bonding member
(main terminal 4, signal terminal 5) together using an ultrasonic
wave, which is characterized by comprising: the ultrasonic bonding
machine 20 having the ultrasonic tool 21 for applying the
ultrasonic wave to the bonding target member (wiring pattern 10)
mounted on a fixed object (power semiconductor device 1) fixed to a
jig (lower jig 24), while pressing the bonding member (main
terminal 4, signal terminal 5) against the bonding target member;
and the bonding inspection apparatus 30 for inspecting a bonding
quality of the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5). The bonding
inspection apparatus 30 of the ultrasonic bonding apparatus 50 is
characterized by comprising: the bonded-state measuring device 31
that is fixed to the jig (lower jig 24) and provided for detecting
a sound propagating in the jig (lower jig 24) to thereby output the
detection signal sig1; and the bonded-state determination device 32
for determining, in a bonding process for the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5), a bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5), on the basis of the detection signal sig 1 outputted
by the bonded-state measuring device 31. According to the
ultrasonic bonding apparatus 50 of Embodiment 1, because of these
characteristics, the bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) is determined based on the detection signal sig 1
outputted by the bonded-state measuring device 31 in the bonding
process. Thus, it is possible to inspect the bonding quality in
real-time in the bonding process, and to reduce time taken for the
quality inspection, and further to accurately determine whether the
quality is defective or not.
[0112] The ultrasonic bonding inspection method of Embodiment 1 is
an ultrasonic bonding inspection method for inspecting a bonding
quality of the bonded portion obtained by bonding between a bonding
target member (wiring pattern 10) mounted on a fixed object (power
semiconductor device 1) fixed to a jig (lower jig 24), and a
bonding member (main terminal 4, signal terminal 5) using an
ultrasonic wave. The ultrasonic bonding inspection method of
Embodiment 1 is characterized by including: a detection signal
monitoring step of detecting, in the bonding process for the
bonding target member (wiring pattern 10) and the bonding member
(main terminal 4, signal terminal 5), a sound propagating in the
jig (lower jig 24), to thereby output a detection signal sig1; and
a bonded-state determination step of determining a bonded state
between the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5) on the basis of
the detection signal sig1 outputted in the detection signal
monitoring step. According to the ultrasonic bonding inspection
method of Embodiment 1, because of these characteristics, the
bonded state between the bonding target member (wiring pattern 10)
and the bonding member (main terminal 4, signal terminal 5) is
determined based on the detection signal sig 1 outputted in the
detection signal monitoring step executed in the bonding process.
Thus, it is possible to inspect the bonding quality in real-time in
the bonding process, and to reduce time taken for the quality
inspection, and further to accurately determine whether the quality
is defective or not.
[0113] In another aspect, the ultrasonic bonding apparatus 50 of
Embodiment 1 is an ultrasonic bonding apparatus for bonding a
bonding target member (wiring pattern 10) and a bonding member
(main terminal 4, signal terminal 5) together using an ultrasonic
wave, which is characterized by comprising: the ultrasonic bonding
machine 20 having the ultrasonic tool 21 for applying the
ultrasonic wave to the bonding target member (wiring pattern 10)
mounted on a fixed object (power semiconductor device 1) fixed to a
jig (lower jig 24), while pressing the bonding member (main
terminal 4, signal terminal 5) against the bonding target member;
and the bonding inspection apparatus 30 for inspecting a bonding
quality of the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5). The bonding
inspection apparatus 30 of the ultrasonic bonding apparatus 50 is
characterized by comprising: the bonded-state measuring device 31
for detecting a vibration propagating in the jig (lower jig 24) or
the housing 28 of the ultrasonic bonding machine 20 equipped with
the jig (lower jig 24), using a sensor (AE sensor 33) that is fixed
to the jig (lower jig 24) or the housing 28 at a position at which
it does not make contact with the bonding target member (wiring
pattern 10) and the bonding member (main terminal 4, signal
terminal 5) and that detects the vibration, to thereby output a
detection signal sig1; and the bonded-state determination device 32
for determining, in a bonding process for the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5), a bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5), on the basis of the detection signal sig1 outputted by
the bonded-state measuring device 31. According to the ultrasonic
bonding apparatus 50 of Embodiment 1, because of these
characteristics, the bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) is determined based on the detection signal sig 1
outputted by the bonded-state measuring device 31 in the bonding
process. Thus, it is possible to inspect the bonding quality in
real-time in the bonding process, and to reduce time taken for the
quality inspection, and further to accurately determine whether the
quality is defective or not.
[0114] In another aspect, the ultrasonic bonding inspection method
of Embodiment 1 is an ultrasonic bonding inspection method for
inspecting a bonding quality of the bonded portion obtained by
bonding between a bonding target member (wiring pattern 10) mounted
on a fixed object (power semiconductor device 1) fixed to a jig
(lower jig 24), and a bonding member (main terminal 4, signal
terminal 5) using an ultrasonic wave. The ultrasonic bonding
inspection method of Embodiment 1 is characterized by including: a
detection signal monitoring step of detecting, in the bonding
process for the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5), a vibration
propagating in the jig (lower jig 24) or the housing 28 of the
ultrasonic bonding machine 20 equipped with the jig (lower jig 24),
to thereby output a detection signal sig1; and a bonded-state
determination step of determining a bonded state between the
bonding target member (wiring pattern 10) and the bonding member
(main terminal 4, signal terminal 5) on the basis of the detection
signal sig1 outputted in the detection signal monitoring step.
According to the ultrasonic bonding inspection method of Embodiment
1, because of these characteristics, the bonded state between the
bonding target member (wiring pattern 10) and the bonding member
(main terminal 4, signal terminal 5) is determined based on the
detection signal sig1 outputted in the detection signal monitoring
step executed in the bonding process. Thus, it is possible to
inspect the bonding quality in real-time in the bonding process,
and to reduce time taken for the quality inspection, and further to
accurately determine whether the quality is defective or not.
[0115] When, as in Patent Document 3, the vibration sensor such as
an AE sensor, etc. is caused to abut on the bonding target member
or the bonding member included in the product, or a vibration
transmission member that intermediates between the target member or
the bonding member and the ultrasonic tool 21 serving to press the
bonding target member or the bonding member, is provided and the
vibration sensor is attached to that vibration transmission member,
the sensor will be removed easily because of the product vibrating
due to the application energy at the time of the ultrasonic
bonding; thus, it is difficult to do so. When the vibration sensor
is mechanically attached using a screw or the like, the bonding
target member or the bonding member may make partial contact with
the sensor to develop a space therebetween, resulting in decreased
detection accuracy. When it is attached adhesively or likewise,
there is a problem that a material used at the time of attachment
causes residue inside the product. Further, in the case where a
portion to be bonded is placed inside a power module, it is
difficult to attach the vibration sensor thereto because an insert
case covering the outside of the power module stands as an
obstacle. When the method of attaching the AE sensor 33 according
to this embodiment is used, it becomes unnecessary to attach the
sensor to the product including the bonding target member and the
bonding member, as a whole. Further, it is difficult to provide the
vibration transmission member that intermediates between the target
member or the bonding member and the ultrasonic tool 21 serving to
press the bonding target member or the bonding member, and to
attach the vibration sensor to that vibration transmission member,
as in Patent Document 3.
[0116] The reason is that the sensor will be removed easily because
of the vibration transmission member strongly vibrating due to the
application energy at the time of the ultrasonic bonding.
[0117] An attached position of the AE sensor 33 only has to have a
continuous relation to the jig to which an object to be bonded is
fixed. For example, when, like in FIG. 24, the AE sensor 33 is
placed on a housing of the facility, namely, the housing 28 of the
ultrasonic bonding machine 20, an adequate AE signal can also be
detected. Further, when, like in FIG. 25, the AE sensor 33 is
placed on the top side or the back side of the movable stage 26 of
the ultrasonic bonding machine 20, an adequate AE signal can also
be detected. FIG. 24 is a diagram showing another ultrasonic
bonding apparatus according to Embodiment 1 of the invention, and
FIG. 25 is a diagram showing still another ultrasonic bonding
apparatus according to Embodiment 1 of the invention. In FIG. 25,
an example is shown in which the AE sensor 33 is attached to a back
surface of a top board 80 of the housing 28, namely, to its surface
on the side opposite to its surface on which the power
semiconductor device 1 is placed. In FIG. 24, an example is shown
in which the AE sensor 33 is attached to a side surface of the
movable stage 26. The reason why the attached position of the AE
sensor 33 only has to have a continuous relation to the jig, is
that acoustic emission is nearly not attenuated inside a material
in a continuous relation to the jig. In particular, when the
material in a continuous relation to the jig is metal, attenuation
of acoustic emission is extremely small, so that the material of
the housing, etc. of the facility is desired to be metal. When the
AE sensor 33 is attached to the top surface or the side surface of
the movable stage 26, it is desired that a metal material be used
as the material of the movable stage 26. When, as shown in FIG. 25,
the top board 80 as a part of the housing 28 intermediates between
the AE sensor 33 and the movable stage 26, it is desired that a
metal material be used as the material of the top board 80.
However, when the ultrasonic horn for generating the ultrasonic
wave is attached to the housing of the facility, acoustic emission
from that housing may possibly be detected. Even in this case, when
the distance to the AE sensor 33 from a position in the housing at
which the jig is fixed, is set less than the distance to the AE
sensor 33 from a position in the housing at which the ultrasonic
horn is attached, acoustic emission from the jig can be detected
accurately.
[0118] Further, when the AE sensor 33 is attached to a surface of
the upper jig 25, an adequate AE signal can also be detected. The
upper jigs are generally provided at two places on both sides of
the product, or at four places on both upper and lower lateral
sides or four corners thereof. When the multiple AE sensors 33 are
attached to the respective jigs and then, the time taken for the AE
signal to reach each of the sensors from the initiation of
application of ultrasonic vibration, or the amplitude thereof, is
monitored, it is possible to specify the position of the jig by
which fixing is insufficient. Namely, when fixing is insufficient,
a fixed area between the product and the jig becomes smaller, so
that it takes time until arrival of the signal and the amplitude is
attenuated. Thus, based on these facts, it is possible to
immediately specify the position of the upper jig by which fixing
is insufficient, while determining whether defective or not.
[0119] Further, when the AE sensor 33 is attached near the ground
on which the facility is placed, it picks up a noise from another
facility, etc., in some cases. In these cases, when a rubber or the
like is attached on the installation surface (bottom surface) of
the facility, it becomes possible to attenuate the signal from the
other facility, etc. Further, at the time of determination on the
detection signal sig1, with the provision of a bandpass filter, it
is possible to eliminate an external frequency that causes a noise.
Note that, when energy of the vibration at the time of ultrasonic
bonding is large, it is not allowed to attach the AE sensor 33 to
the ultrasonic tool 21 because the AE sensor 33 will be removed or
broken.
[0120] In the case of bonding the bonding target member (wiring
pattern 10) and the bonding member (main terminal 4, signal
terminal 5) together, in order to achieve an adequate bonding
strength, it is required to apply ultrasonic energy around the
bonding interface between the bonding target member (wiring pattern
10) and the bonding member (main terminal 4, signal terminal 5).
When the product (power semiconductor device 1) is insufficiently
fixed by the jig (upper jig 24, lower jig 25) or the ultrasonic
tool 21 is attached loosely, no adequate bonding strength is
achieved. Insufficient fixing by the jig is assumed to be due to
warpage of the product, warpage or deterioration of the jig,
deterioration or insufficient torque of the screw for fixing, or
the like. It is assumed to be due to partial contact of the
contacting surface, deterioration of the contacting surface, or the
like, when the upper jig 25 is used for fixing the product (power
semiconductor device 1). The AE signal is characterized in that the
frequencies of AE signals generated due to these respective factors
are different from each other. When the AE signal at the time of
ultrasonic bonding is detected using the AE sensor 33 and the
frequency of the AE signal is monitored on a time axis, it is
possible to immediately identify the factor for reducing the
strength. When it is difficult to make identification because a
frequency difference is slight, it is possible, by placing the AE
sensors at plural positions on the lower jig 24, to identify the
factor according to phase differences or amplitude levels of the AE
signals individually detected by them.
[0121] Further, it is possible to determine whether the bonding is
defective or not, according to a difference in phase (phase
difference) between the waveform of the applied ultrasonic wave and
the waveform of the AE signal. Namely, if the phase difference is
small, this means that the application energy at the time of
ultrasonic bonding is properly applied toward the bonding interface
and the AE signal at that instance is properly transmitted from the
jig to the AE sensor 33. In contrast, if the phase difference is
large, this is because a pathway through which the AE signal is
transmitted has been extended due to a gap placed beneath the
bonded portion and between the product and the jig, or the like, to
thereby increase the time taken to reach the AE sensor 33.
Accordingly, if the phase difference is large, this means that the
energy of the ultrasonic wave is not properly applied toward the
bonding interface.
Embodiment 2
[0122] An ultrasonic bonding apparatus 50 of Embodiment 2 according
to the invention will be described. In the ultrasonic bonding
apparatus 50 of Embodiment 2, its bonded-state measuring device 31
differs from that in Embodiment 1. FIG. 23 is a diagram showing the
bonded-state measuring device according to Embodiment 2 of the
invention. Other than the bonded-state measuring device 31, the
ultrasonic bonding apparatus 50 of Embodiment 2 is the same as the
above, so that description will be made about the bonded-state
measuring device 31.
[0123] What differs from Embodiment 1 is that, using a laser
Doppler vibrometer 56 as a non-contact vibrometer, a laser is
radiated to the ultrasonic tool 21 provided as a measuring target
(subject to monitoring) to thereby measure a vibration. The
bonded-state measuring device 31 in Embodiment 2 comprises: the
laser Doppler vibrometer 56; a laser reflective mirror 57; a
measuring device 55 for measuring a signal detected by the laser
Doppler vibrometer 56 (signal containing information about the
vibration of the measuring target); and a data logger 58 for
recording data measured by the measuring device 55.
[0124] The laser Doppler vibrometer 56 detects a velocity and a
displacement of the vibration at a point irradiated by the laser.
The measuring device 55 outputs the signal detected by the laser
Doppler vibrometer (signal containing information about the
vibration of the measuring target) as a detection signal sig1, to
the bonded-state determination device 32.
[0125] When, using the laser Doppler vibrometer 56, the laser is
radiated to the ultrasonic tool 21 to thereby measure the
vibration, it is possible to determine whether the bonding quality
of the bonding member (main terminal 4, signal terminal 5) and the
bonding target member (wiring pattern 10) is defective or not.
Specifically, it is possible to determine whether the bonding
quality is defective or not, according to a difference between: a
vibration displacement amount corresponding to a necessary bonded
area (reference displacement amount) with respect to the bonded
area between the bonding member (main terminal 4, signal terminal
5) and the bonding target member (wiring pattern 10); and a
measured vibration displacement amount (measured displacement
amount). When the difference between the reference displacement
amount and the measured displacement amount is within a threshold
value, the bonded state is determined to be non-defective. When the
difference between the reference displacement amount and the
measured displacement amount exceeds the threshold value, the
bonded state is determined to be defective (bad). Because the
displacement amount is measured in this manner, the ultrasonic
bonding apparatus 50 of Embodiment 2 is characterized by being
capable of recognizing a vibration state more quantitatively than
the ultrasonic bonding apparatus 50 of Embodiment 1. According to
the ultrasonic bonding apparatus 50 of Embodiment 2, like in the
ultrasonic bonding apparatus 50 of Embodiment 1, it is unnecessary
to attach a detector (the laser Doppler vibrometer 56) of the
bonded-state measuring device 31 to the product because the bonded
state of the product is inspected in a contactless manner. Thus, it
is possible to make the inspection time shorter than that in the
case where the inspection is performed in a manner that a tester is
made in contact with the product.
[0126] When the terminal (main terminal 4, signal terminal 5) to be
ultrasonically bonded is monitored together with the ultrasonic
tool 21, a following effect will be achieved. For example, when the
terminal (main terminal 4, signal terminal 5) is monitored after
the monitoring of the ultrasonic tool 21, if the ultrasonic tool 21
and the terminal are in the same vibration state, it may be
confirmed that the ultrasonic tool 21 could have properly applied
an ultrasonic vibration to the terminal. If the terminal is smaller
in vibration than the ultrasonic tool 21, it may be confirmed that
abrasion occurred between the head of the ultrasonic tool 21 and
the terminal and thus the tool could not have properly applied an
ultrasonic vibration to the terminal. Due to that abrasion, copper
swarf may be produced in some cases, so that it is possible to
determine whether a removal process of the copper swarf is
necessary or not, according to the vibration monitoring result.
Further, when the terminal becomes smaller in vibration than the
ultrasonic tool 21 because of the influence of individual
differences between the products, for example, differences in
warpage of the terminal or the like, this monitoring result is fed
back, whereby the bonding condition is changed during ultrasonic
bonding so that their vibration states become the same, for
example, in a manner that the applied load is increased, or the
like. This makes it possible to achieve a proper bonding quality
while reducing the production of copper swarf to the minimum.
Further, when the vibration of the circuit board 8 is also
monitored and the vibrations of the terminal and the circuit board
8 are monitored concurrently with the vibration of the ultrasonic
tool 21, an effect similar to the above can also be exerted.
[0127] With respect to the product, even when a measurement
position at which a vibration is measured through laser radiation,
is not on the ultrasonic tool 21, but on the bonding target member
(wiring pattern 10), the bonding member (main terminal 4, signal
terminal 5) or the jig (lower jig 24, upper jig 25) for fixing the
product (power semiconductor device 1), an effect similar to the
above will be exerted. When the AE signal shown in Embodiment 1 is
used in combination, a new effect shown below will be exerted. When
the inspection is performed using both of the AE signal by the AE
sensor 33 described in Embodiment 1 and a vibration signal by the
laser Doppler vibrometer described in Embodiment 2, it is possible
to determine whether the bonding quality is defective or not, more
highly accurately. Namely, whether or not the vibration of the
ultrasonic tool 21 has been properly transmitted to the
ultrasonically bonded portion 17, 18 can be inspected using the
laser Doppler vibrometer, and further, whether or not friction at
the interface between the bonding target member and the bonding
member is normal, and whether or not the fixing of the product is
normal, can be inspected using the AE signal detected by the AE
sensor 33. This provides an advantage that the accuracy of the
determination as to whether the bonding quality is defective or
not, becomes much higher.
[0128] As described above, the ultrasonic bonding apparatus 50 of
Embodiment 2 is an ultrasonic bonding apparatus for bonding a
bonding target member (wiring pattern 10) and a bonding member
(main terminal 4, signal terminal 5) together using an ultrasonic
wave, which is characterized by comprising: the ultrasonic bonding
machine 20 having the ultrasonic tool 21 for applying the
ultrasonic wave to the bonding target member (wiring pattern 10)
mounted on a fixed object (power semiconductor device 1) fixed to a
jig (lower jig 24), while pressing the bonding member (main
terminal 4, signal terminal 5) against the bonding target member;
and the bonding inspection apparatus 30 for inspecting a bonding
quality of the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5). The bonding
inspection apparatus 30 of the ultrasonic bonding apparatus 50 is
characterized by comprising: the bonded-state measuring device 31
for detecting a vibration of a measuring object vibrated by the
ultrasonic wave, to thereby output the detection signal sig1; and
the bonded-state determination device 32 for determining, in a
bonding process for the bonding target member (wiring pattern 10)
and the bonding member (main terminal 4, signal terminal 5), a
bonded state between the bonding target member (wiring pattern 10)
and the bonding member (main terminal 4, signal terminal 5), on the
basis of the detection signal sig1 outputted by the bonded-state
measuring device 31. According to the ultrasonic bonding apparatus
50 of Embodiment 2, because of these characteristics, the bonded
state between the bonding target member (wiring pattern 10) and the
bonding member (main terminal 4, signal terminal 5) is determined
based on the detection signal sig1 outputted by the bonded-state
measuring device 31 in the bonding process. Thus, it is possible to
inspect the bonding quality in real-time in the bonding process,
and to reduce time taken for the quality inspection, and further to
accurately determine whether the quality is defective or not.
[0129] The ultrasonic bonding inspection method of Embodiment 2 is
an ultrasonic bonding inspection method for inspecting a bonding
quality of the bonded portion obtained by bonding between a bonding
target member (wiring pattern 10) mounted on a fixed object (power
semiconductor device 1) fixed to a jig (lower jig 24), and a
bonding member (main terminal 4, signal terminal 5) using an
ultrasonic wave. The ultrasonic bonding inspection method of
Embodiment 2 is characterized by including: a detection signal
monitoring step of detecting, in the bonding process for the
bonding target member (wiring pattern 10) and the bonding member
(main terminal 4, signal terminal 5), a vibration of a measuring
object vibrated by the ultrasonic wave, to thereby output a
detection signal sig1; and a bonded-state determination step of
determining a bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) on the basis of the detection signal sig1 outputted in
the detection signal monitoring step. According to the ultrasonic
bonding inspection method of Embodiment 2, because of these
characteristics, the bonded state between the bonding target member
(wiring pattern 10) and the bonding member (main terminal 4, signal
terminal 5) is determined based on the detection signal sig1
outputted in the detection signal monitoring step executed in the
bonding process. Thus, it is possible to inspect the bonding
quality in real-time in the bonding process, and to reduce time
taken for the quality inspection, and further to accurately
determine whether the quality is defective or not.
Embodiment 3
[0130] In Embodiment 3, description will be made about the cases
where the ultrasonic bonding apparatus and the ultrasonic bonding
inspection method in Embodiment 1 or Embodiment 2 are applied
respectively to a wire bonding apparatus for bonding a connecting
wire 15 in the product (power semiconductor device 1) and a wire
bonding inspection method for inspecting a wire bonding portion
after bonding that is an ultrasonically-bonded portion. The wire
bonding apparatus is an apparatus for bonding a wire (corresponding
to the bonding member) to an object to be bonded (corresponding to
the bonding target member), by pressure bonding using ultrasonic
vibration. The wire is made of Al with a diameter of 100 to 500
.mu.m, or Au or Ag with a diameter of 10 to 50 .mu.m. The summary
of its configuration, the analysis on its detection signal sig1,
and the feedback method to the apparatus on the basis of the
detection signal sig1, are almost the same as in the ultrasonic
bonding apparatus 50 shown in Embodiment 1. A frequency of 40 to
120 kHz is used that is higher than that by the ultrasonic bonding
machine 20 in the ultrasonic bonding apparatus 50 of Embodiment 1
or Embodiment 2. The amplitude is about 1 to 5 .mu.m that is
smaller than that by the ultrasonic bonding machine 20 in
Embodiment 1 or Embodiment 2. Namely, the frequency and the
amplitude used in the wire bonding apparatus are high and small,
respectively. In order to detect the vibration of the bonded
portion between the bonding target member and the bonding member
(connecting wire 15) that is caused by such a high-frequency and
small-amplitude ultrasonic wave, the AE signal is well-suited. For
example, the wire bonding apparatus as the ultrasonic bonding
apparatus 50 of Embodiment 3 ultrasonically bonds the connecting
wires 15a, 15b and 15c shown in FIG. 5 to the bonding target
members (wiring patterns 10a, 10b and 10d, electrode of the IGBT
12, and electrode of the FwDi 13).
[0131] The reason why, in the wire bonding process using the wire
bonding apparatus, namely, the ultrasonic bonding process using the
ultrasonic bonding apparatus 50 of Embodiment 3, the AE signal is
well-suited to the inspection of wire bonding and confirmation of
the state of the wire bonding apparatus, will be described. The
reason is that the width of the ultrasonic tool used in wire
bonding is smaller than the width (5 to 10 mm) of the ultrasonic
tool used in ultrasonic bonding of the main terminal 4 or the
signal terminal 5. The ultrasonic tool for wire bonding the 100 to
500 .mu.m Al wire has a width of 1 to 2 mm. Further, the ultrasonic
tool for wire bonding the 10 to 50 .mu.m Au/Ag wire has a width of
1 mm or less. Accordingly, the diameter of the wire is small while
the cross-section of the wire has a circular shape, so that, with
the wire bonding apparatus whose ultrasonic tool is small in width,
it is difficult when the laser Doppler vibrometer is used, to
radiate the laser to a target spot. Further, if the laser could be
radiated thereto, it is difficult to cause the laser to be
reflected perpendicularly, making it hard to detect the reflected
laser. Furthermore, while a variety of materials, such as metal,
ceramic and the like may be employed for the ultrasonic tool, such
a material is chosen as the material of the ultrasonic tool that is
adequate in view of bondability between the object to be bonded and
the wire, so that, in many cases, it can not reflect the laser
originally. Because of these reasons, it is required to detect the
vibration of the ultrasonically-bonded portion between the object
to be bonded and the wire in the wire bonding process, by a method
other than that using the laser Doppler vibrometer. In such a case,
it is well-suited to detecting the AE signal, for example, by
attaching the AE sensor 33 on the jig, namely, on the outer surface
of the jig.
[0132] A wire bonding condition employed in the wire bonding
apparatus as the ultrasonic bonding apparatus 50 of Embodiment 3 is
shown in FIG. 26. FIG. 26 is a diagram showing the wire bonding
condition employed in the wire bonding apparatus according to
Embodiment 3 of the invention. The main condition is represented by
a load (magnitude of the applied force), power (applied energy) and
time. In general, the load and the power are varied in two stages,
and in an initial stage of bonding, an initially-bonded portion
(portion serving as a nucleus) is formed using low load and power,
and in a later stage of bonding, the load and the power are
increased to thereby increase the bonded area. In FIG. 26, an
example of the wire bonding condition is shown in which a weak load
and low power are applied until Time t1 and thereafter, the load
and the power are gradually increased until Time ta1. On this
occasion, the frequency of the ultrasonic wave applied in the
facility, namely, the ultrasonic bonding machine 20, is monitored
and feedback-controlled, so that the frequency of the applied
ultrasonic wave in the later stage is higher by several kHz than
that in the initial stage. The wire bonding process includes an
application-frequency changing step of increasing the application
frequency of the ultrasonic wave to be applied by the ultrasonic
tool 21 of the ultrasonic bonding machine 20 to the bonding target
member (wiring patterns 10a, 10b and 10d, electrode of the IGBT 12,
and electrode of the FwDi 13) and the bonding member (connecting
wires 15a, 15b and 15c).
[0133] When a foreign substance (examples include an invisible
substance such as oil, etc.) is present on the wiring pattern 10,
the bonded area of the ultrasonically bonded portion will finally
be reduced. Accordingly, the progress of the bonding is slow, and
in that case, the timing at which the frequency of the ultrasonic
wave to be applied in the later stage of bonding varies will be
later than a normal one. When the timing at which the frequency
varies is detected using the AE sensor 33, it becomes possible to
easily determine whether the bonding of the ultrasonically bonded
portion is defective or not.
[0134] Using FIG. 27 to FIG. 29, how to determine whether bonding
is defective or not in the ultrasonic bonding inspection method of
Embodiment 3, will be described. FIG. 27 is a diagram for
illustrating how to determine whether bonding is defective or not
in the ultrasonic bonding inspection method according to Embodiment
3 of the invention. FIG. 28 is a diagram for illustrating a case
where bonding is determined to be non-defective by the ultrasonic
bonding inspection method according to Embodiment 3 of the
invention, and FIG. 29 is a diagram for illustrating a case where
bonding is determined to be defective by the ultrasonic bonding
inspection method according to Embodiment 3 of the invention. In
FIG. 27, an application frequency waveform 81 of the ultrasonic
wave to be applied and a detection frequency waveform 82 detected
by the AE sensor 33 are shown. The detection frequency is, for
example, the frequency f1 that is the same as a frequency of the
ultrasonic horn 22 obtained through numerical arithmetic
processing. In FIG. 27, the abscissa represents time, and the
ordinate represents the application frequency or the detection
frequency. The application frequency waveform 81 is an example in
which, like the application energy or the applied force in FIG. 26,
the frequency is weak as a first frequency until Time t1, and
thereafter the frequency gradually increases until Time ta1 to
reach a high frequency as a second frequency at Time ta1. The
detection frequency waveform 82 detected by the AE sensor 33 is an
example in which the frequency is weak as a first frequency until
Time t2, the frequency begins to increase at Time t2 and the
frequency gradually increases until Time ta2 to reach a high
frequency as a second frequency at Time ta2. A detection frequency
waveform 82a in FIG. 28 is a detection frequency waveform in the
case where bonding of the ultrasonically bonded portion is
non-defective, and a detection frequency waveform 82b in FIG. 29 is
a detection frequency waveform in the case where bonding of the
ultrasonically bonded portion is defective.
[0135] A time difference between Time t1 and Time t2, namely,
.DELTA.t1 as a delay time resulting from subtracting Time t1 from
Time t2, is an initial time difference (delay time) in varying
frequency. A time difference between Time ta1 and Time ta2, namely,
.DELTA.t2 as a delay time resulting from subtracting Time ta1 from
Time ta2, is a final time difference (delay time) in varying
frequency. Whether the bonding of the ultrasonically bonded portion
is defective or not can be determined by using the initial time
difference .DELTA.t1 in varying frequency or the final time
difference .DELTA.t2 in varying frequency. Determination as to
whether the bonding of the ultrasonically bonded portion is
defective or not is executed in the bonded-state determination step
as Step S003 shown in FIG. 10, FIG. 16, FIG. 19, FIG. 20 or FIG.
21.
[0136] First, an example of using the initial time difference
.DELTA.t1 in varying frequency will be described. In the
determination as to whether the bonding of the ultrasonically
bonded portion is defective or not, namely, in the bonded-state
determination step of determining the bonded state of the
ultrasonically bonded portion, the bonded-state determination
device 32 generates the detection frequency waveform 82 (frequency
waveform) to be obtained through calculation from the waveform of
the detection signal sig1 measured by the AE sensor 33. When a
difference (time difference .DELTA.t1) between a timing (Time t2)
at which the frequency varies in the detection frequency waveform
82 (detection frequency waveform 82b in FIG. 29) and a timing (Time
t1) at which the frequency varies in the application frequency
waveform 81, is more than a determination value tr1 given as a
preset threshold value, the bonded-state determination device 32
determines that the bonded state of the ultrasonically bonded
portion is defective. In contrast, when a difference (time
difference .DELTA.t1) between a timing (Time t2) at which the
frequency varies in the detection frequency waveform 82 (detection
frequency waveform 82a in FIG. 28) and a timing (Time t1) at which
the frequency varies in the application frequency waveform 81, is
equal to or less than the preset determination value tr1, the
bonded-state determination device 32 determines that the bonded
state of the ultrasonically bonded portion is non-defective.
[0137] Next, an example of using the final time difference
.DELTA.t2 in varying frequency will be described.
[0138] In the determination as to whether the bonding of the
ultrasonically bonded portion is defective or not, namely, in the
bonded-state determination step of determining the bonded state of
the ultrasonically bonded portion, the bonded-state determination
device 32 generates the detection frequency waveform 82 (frequency
waveform) to be obtained through calculation from the waveform of
the detection signal sig1 measured by the AE sensor 33. When a
difference (time difference .DELTA.t2) between a timing (Time ta2)
at which the frequency varies in the detection frequency waveform
82 (detection frequency waveform 82b in FIG. 29) and a timing (Time
ta1) at which the frequency varies in the application frequency
waveform 81, is more than a determination value tr2 given as a
preset threshold value, the bonded-state determination device 32
determines that the bonded state of the ultrasonically bonded
portion is defective. In contrast, when a difference (time
difference .DELTA.t2) between a timing (Time ta2) at which the
frequency varies in the detection frequency waveform 82 (detection
frequency waveform 82a in FIG. 28) and a timing (Time ta1) at which
the frequency varies in the application frequency waveform 81, is
equal to or less than the preset determination value tr2, the
bonded-state determination device 32 determines that the bonded
state of the ultrasonically bonded portion is non-defective.
[0139] Furthermore, detection and feedback of a varying timing in
the detection frequency waveform 82 allows increasing or decreasing
the bonding time. This makes it possible to achieve an
ultrasonically bonded portion having an excellent bonding strength.
Such a method of executing the bonding process by changing the
bonding condition based on whether the bonding of the
ultrasonically bonded portion is defective or not, is similar to in
the flowchart shown in FIG. 16. For the wire bonding process using
the wire bonding apparatus, it suffices to read "terminal bonding"
in the flowchart shown in FIG. 16, differently as "wire-end
bonding". The flowchart shown in FIG. 16 with such a different
reading will be described. In Step S001, product introduction is
done. In Step S002, a first wire end, for example, a right-side
wire end of the connecting wire 15a in FIG. 5, is subjected to
ultrasonic bonding and the detection signal sig1 is monitored by
the bonded-state measuring device 31 (detection signal monitoring
step).
[0140] In Step S003, based on the detection signal sig1, the
bonded-state determination device 32 determines the bonded state
between the first wire end as the bonding member and the wiring
pattern 10 as the bonding target member (bonded-state determination
step). When, in Step S003, the bonded state is determined to be
non-defective, the flow moves to Step S004. When, in Step S003, the
bonded state is determined to be defective (bad), the flow moves to
Step S007. In Step S007, whether the condition is changeable or not
is determined (bonding condition determination step), and when it
is determined to be changeable, the bonding condition is changed in
Step S008 (bonding condition changing step), and then the flow
returns to Step S002. When the condition is determined to be not
changeable in Step S007, the flow terminates (defective bonding
terminating step). Note that when the bonding condition changing
step as Step S008 has been executed, the detection signal
monitoring step as Step S002 and the bonded-state determination
step as Step S003 to be executed in the ultrasonic bonding
condition changed in the bonding-condition changing step,
correspond to a bonding continuing step.
[0141] In Step S004, the wire-end bonding in operation is stopped
(ultrasonic-wave application stopping step), and then the flow
moves to Step S005. Note that the ultrasonic-wave application
stopping step as Step S004 is also a non-defective bonding stopping
step in which, when the bonded state between the bonding target
member (wiring patterns 10a, 10b and 10d, electrode of the IGBT 12,
and electrode of the FwDi 13) and the bonding member (connecting
wires 15a, 15b and 15c) is determined to be non-defective in the
bonded-state determination step as Step S003, the bonding process
in operation for the bonding target member and the bonding member
is stopped. In Step S005, it is determined whether or not bonding
has been completed for all wire ends. When it is determined in Step
S005 that a wire end to be bonded as the bonding member still
remains, namely, bonding has not been completed, the flow returns
to Step S002, whereas when it is determined that no wire end to be
bonded remains, namely, bonding has been completed for all wire
ends, the flow moves to Step S006. In the example shown in FIG. 5,
six wire ends are provided, so that Steps S002 to S005 are executed
six times. In Step S006, the product is discharged (product
discharging step), so that the flow terminates. In Step S006, the
upper jigs 25 are removed and the intermediate product of the power
semiconductor device 1 is discharged from the ultrasonic bonding
machine 20. When the bonding process for the intermediate product
of one power semiconductor device 1 has been completed, the bonding
process for an intermediate product of the next power semiconductor
device 1 is executed.
[0142] It is noted that, when "terminal bonding" in the flowcharts
in FIG. 10, FIG. 19, FIG. 20 and FIG. 21 is read differently as
"wire-end bonding", it is also possible to execute the wire bonding
process using the wire bonding apparatus, according to each of
these flowcharts.
[0143] Further, in order to achieve an ultrasonically bonded
portion having an adequate bonding strength, it is required to
apply ultrasonic energy around the bonding interface between the
wiring pattern 10 and the connecting wire 15. When the product is
insufficiently fixed by the jig or the ultrasonic tool is attached
loosely, an ultrasonically bonded portion having an adequate
bonding strength is not achieved. Insufficient fixing by the jig is
assumed to be due to warpage of the product, warpage or
deterioration of the jig, deterioration or insufficient torque of
the screw for fixing, or the like. It is assumed to be due to
partial contact of the contacting surface, deterioration of the
contacting surface, or the like, when the upper jig 25 is used for
fixing the product (power semiconductor device 1). The AE signal is
characterized in that the frequencies of AE signals generated due
to these respective factors are different from each other. When the
AE signal at the time of wire bonding is detected using the AE
sensor 33 and the frequency of the AE signal is monitored on a time
axis, it is possible to immediately identify the factor for
reducing the strength of the ultrasonically bonded portion. When it
is difficult to make identification because a frequency difference
is slight, it is possible, by placing the AE sensors 33
respectively on the lower jig 24 at plural positions and on the
outer surface of the ultrasonic horn 22, to identify the factor
according to phase differences or amplitude levels of the AE
signals individually detected by them. In the case of the wire
bonding apparatus, the application energy of the ultrasonic wave to
be applied is lower than that of the ultrasonic bonding apparatus
50 in Embodiments 1 and 2, so that the AE sensor 33 is allowed to
be placed on the outer surface of the ultrasonic horn 22. Note that
the AE sensor 33 is not allowed to be attached to the ultrasonic
tool of the wire bonding apparatus. This is because, when the AE
sensor 33 is attached to the ultrasonic tool that is light, its
weight is changed, so that the vibration state of the ultrasonic
tool varies.
[0144] Further, it is possible to determine whether the bonding is
defective or not, according to a difference in phase (phase
difference) between the waveform of the applied ultrasonic wave and
the waveform of the AE signal. Namely, if the phase difference is
small, this means that the application energy at the time of
ultrasonic bonding is properly applied toward the bonding
interface, and the AE signal at that instance is properly
transmitted from the jig to the AE sensor 33. In contrast, if the
phase difference is large, this is because a pathway through which
the AE signal is transmitted has been extended due to a gap placed
beneath the bonded portion and between the product and the jig, or
the like, to thereby increase the time taken to reach the AE sensor
33. Accordingly, if the phase difference is large, this means that
the energy of the ultrasonic wave is not properly applied toward
the bonding interface.
[0145] It is noted that, in the respective embodiments, the power
semiconductor element mounted in the power semiconductor device 1
is described as it is exemplified by the IGBT as a switching
element and the FwDi as a rectifier element; however, it may be
another switching element such as a MOSFET (Metal Oxide
Semiconductor Field Effect Transistor), etc. or another rectifier
element such as an SBD (Schottky Barrier Diode), etc. Further, the
power semiconductor element mounted in the power semiconductor
device 1 may be a usual element whose base member is a silicon
wafer; however, a so-called wide bandgap semiconductor material may
be used therefor that is wider in bandgap than silicon and is
represented by silicon carbide (SiC), a gallium nitride (GaN)-based
material or diamond. For example, when silicon carbide (SiC), a
gallium nitride (GaN)-based material or diamond is used for the
IGBT 12 serving as a switching element or the FwDi 13 serving as a
rectifier element, because its power loss is lower than that of a
conventionally-used element formed of silicon (Si), the efficiency
of the power semiconductor device 1 can be enhanced. Further,
because the withstanding voltage is high and the allowable current
density is also high, the power semiconductor device 1 can be
downsized. Furthermore, because the wide bandgap semiconductor
element has high heat resistance, it is operable at a high
temperature. This allows a heatsink to be downsized and a water
cooling unit to be substituted with an air cooling one, so that the
power semiconductor device provided with the heatsink can be
further downsized.
[0146] As described previously, because of dealing with large
current, the power semiconductor device 1 is designed to
efficiently dissipate heat and thus, the power semiconductor device
1 using a wide bandgap semiconductor material is also designed to
efficiently dissipate heat. The ultrasonic bonding apparatus 50 in
Embodiment 1, Embodiment 2 and Embodiment 3 can inspect the bonding
quality in real time in the bonding process on the basis of the
detection signal(s) of the AE sensor 33 or/and the laser Doppler
vibrometer 56, without directly monitoring the temperature of the
terminal bonded portion using a thermo-viewer. This makes it
possible to properly perform inspection of the ultrasonic bonding
of the power semiconductor device 1 using the wide bandgap
semiconductor material.
[0147] It is noted that, with respect to the signal input unit 36,
the signal processing unit 37, the arithmetic processing unit 38,
the determination unit 39 and the determination result output unit
40, that are function blocks of the bonded-state determination
device 32, their functions may be implemented by a processor 98 and
a memory 99 shown in FIG. 30. FIG. 30 is a diagram showing a
hardware configuration example for implementing the function blocks
of the bonded-state determination device. In this case, the signal
input unit 36, the signal processing unit 37, the arithmetic
processing unit 38, the determination unit 39 and the determination
result output unit 40 are implemented in such a manner that the
processor 98 executes programs stored in the memory 99. Instead,
plural processors 98 and plural memories 99 may execute the
respective functions in their cooperative manner.
[0148] It should be noted that a combination of the respective
embodiments and an appropriate modification/omission in the
embodiments may be made in the present invention without departing
from the scope of the invention.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0149] 1: power semiconductor device (fixed object), 4: main
terminal (bonding member), 5: signal terminal (bonding member), 10,
10a, 10b, 10c, 10d: wiring pattern (bonding target member), 15,
15a, 15b, 15c: connecting wire (bonding member), 20: ultrasonic
bonding machine, 21: ultrasonic tool, 24: lower jig, 25: upper jig,
28: housing, 30: bonding inspection apparatus, 31: bonded-state
measuring device, 32: bonded-state determination device, 33: AE
sensor, 37: signal processing unit, 38: arithmetic processing unit,
56: laser Doppler vibrometer (non-contact vibrometer), 50:
ultrasonic bonding apparatus, 71: AE signal waveform, 72: AE signal
waveform, 74: arithmetically-processed waveform, 75:
arithmetically-processed waveform, 81: application frequency
waveform, 82, 82a, 82b: detection frequency waveform, sig1:
detection signal, sig2: determination result signal (determination
result), .DELTA.t1, .DELTA.t2: time difference, tr1, tr2:
determination value.
* * * * *